Slow-Roasted Salmon Hits the Spot for a Healthy Weeknight Recipe

The holiday season is in full swing and I’m coming in hot with a favorite!  It’s the perfect combination of healthy whole foods and decadence.  And isn’t that just what we want at this time of year?

Slow-roasted salmon is brilliant in its own right.  The flavor is delicate and the texture, completely unmatched.  But add to it, earthy lentils and peppery arugula, all tied together by a compound butter that becomes the most flavorful, lovely sauce, and well, you’ve got something extraordinary.

But the real flex is in how easy it is to put together.  You see, the compound butter can be put together at any time – days, weeks or even months ahead of time – as they freeze exceptionally well.  And the lentils and salmon cook, pretty much undisturbed, the entire time.  The only thing left to do is chop a leek and dress some arugula.  That’s it!  Your friends and family will think you worked for hours putting this masterpiece together – but don’t worry – your secret is safe with me!

Slow-roasted Salmon with Lentils and Mustard-Tarragon Butter

Serves 4-6



7 Tbsp. unsalted butter, room temperature

1 clove garlic, finely chopped

½ tsp. chili flakes

3 tsp. whole grain mustard

1-2 Tbsp. tarragon, finely chopped

Zest of an orange

2 tsp. juice of an orange

¾ tsp. kosher salt

Black pepper


1 c. French green lentils

4 c. water

Big pinch of salt

1 leek

1 tbsp. butter

2 tsp. juice of orange


2 lb. piece of salmon

1 Tbsp. olive oil

Salt and freshly ground black pepper

5 oz. baby arugula

Drizzle of olive oil


  1. Preheat the oven to 250 degrees.
  2. To prepare the lentils, combine them with 4 cups of water and a large pinch of salt in a saucepan over medium heat.  Once they have reached a boil, reduce the heat to a simmer and cook, uncovered, until the lentils are just tender – about 20-25 minutes.
  3. While the lentils are cooking, place the salmon on a parchment-lined sheet pan and rub it with the olive oil and season it well with salt and pepper.  Place it in the oven to roast for about 35 minutes.  You are just looking for it to start to flake apart when you press into it on top.  It will be soft due to the low-temperature cooking.
  4. Next, make the mustard butter, by adding 7 tablespoons of softened butter into a bowl.  Add to it the finely chopped garlic, chili flakes, mustard, chopped tarragon, orange zest, orange juice, salt and pepper.  Combine everything well by mushing it with the side of a spatula, and then set it aside.
  5. Remove the root end of the leek and slice it lengthwise down the center.  (Remove the outer layers and save them to make stock). Wash both halves of the leek under running water, making sure to get all sand and grit out of all of the layers.  Then place the flat sides of the leek on the cutting board and slice them horizontally into half-circles.
  6. When the lentils are done, drain them and keep ½ cup of the cooking liquid.  
  7. Return the empty pan to the medium heat and add the one tablespoon of butter and the leeks.  Cook the leeks, stirring occasionally, until they are softened and lightly caramelized – about 5 or 6 minutes.
  8. Add the lentils and the reserved cooking liquid to the leeks and stir to combine.
  9. Turn off the heat and add half of the mustard butter to the lentils and stir it through allowing it to melt.  Place a lid on the lentils and set them aside.
  10. When the salmon is done, remove it from the oven and add the remaining mustard butter on top allowing it to melt all over the filet.
  11. In a bowl, add the arugula, a drizzle of extra virgin olive oil and a pinch of salt and toss it together gently.
  12. To plate, line a platter with the dressed arugula.  Next, top with the lentils.  And lastly, flake apart the salmon into large portion-sized chunks, and place them over the lentils.  ENJOY!


  • Want a vegan alternative?  Use vegan butter (Miyoko’s is my favorite)
  • Don’t have French green lentils?  You can use whatever lentils you have.  I prefer the French lentils because they hold their shape and texture better after cooking.
  • Don’t have tarragon, but have other herbs?  No problem, you can easily substitute something else – my preferred substitutions would be thyme, dill and parsley.
  • Don’t have an orange, but have a lemon?  No problem – use it!

Hello, I’m Natalie!  I’m a professionally-trained chef, culinary instructor and recipe developer living in Ann Arbor.  A career change, a trip through culinary school 20 years ago, and being a lifelong Julia Child enthusiast has led me to a career doing my very favorite thing:  making food and cooking approachable to home cooks of all ages!   

My passion for creating great food experiences and getting people excited about learning and having fun in the kitchen is always at the heart of what I do.  You can find me at  And on social media you can find me at @NatalieMarbleCooks.  Sign up for my bi-weekly email newsletter here, where I share family-friendly recipes, tips & tricks, new class information, and hopefully a little inspiration!