Cut the salmon into 4 even fillets. Pat completely dry with paper towels and season both sides with the salt and pepper.

Heat the avocado oil in a large skillet over medium-high heat until it shimmers. Add the salmon skin side up (or presentation side down) and sear without moving for 4 minutes, until a golden crust forms.

Flip the fillets and cook 2 to 4 minutes more, until the thickest part reaches 125 to 130°F. Move the salmon to a plate.

Lower the heat to medium-low. Add the minced garlic and cook 30 seconds, until fragrant.

Pour in the chicken broth and lemon juice and scrape up the browned bits. Simmer about 2 minutes, until reduced by about half.

Take the skillet off the heat. Add the cold butter in pieces and swirl until melted and glossy. Stir in the lemon zest and chopped dill, and taste for salt.

Return the salmon to the pan, spoon the sauce over the top, and serve right away.