In a small mixing bowl, add 2 Tbsp Dijon mustard, 2 Tbsp maple syrup, 2 Tbsp lemon juice, ½ tsp kosher salt, and ¼ tsp black pepper. Whisk to combine.
Slowly pour in 6 Tbsp extra virgin olive oil, whisking as you pour, until the dressing comes together and is smooth.
Taste and adjust seasoning if you'd like. Set aside.
In a mixing bowl, combine 1 lb. skinless salmon filet (that's cut into bite-sized pieces), with 2 Tbsp of the dressing and a pinch of salt and pepper. Let sit while you make the slaw.
To another bowl, add 1 medium to large crisp apple and 1 small fennel bulb (both cored and very thinly sliced), 2 Tbsp lemon juice, and a generous pinch of kosher salt.
Toss the slaw, then let it sit while you continue with the recipe. This will soften it a bit.
Heat a large heavy-bottomed skillet (such as cast iron, ceramic, or stainless) over MED HIGH heat.
Once hot, add a drizzle of olive or avocado oil. Add the salmon pieces in a single layer and cook, 2-3 minutes per side, or until golden brown and cooked through.
Evenly divide the 2 cups cooked farro and 2 cups baby arugula among 4 bowls.
Top bowls with salmon bites, slaw, and ¼ cup chopped walnuts (divided among the 4 bowls). Drizzle with some of the remaining dressing and sprinkle with black pepper if desired.
Serve warm or at room temperature and enjoy!
