If using frozen salmon, thaw it out first. Rinse it and dry it with a paper towel. Place it on a plate and press it with paper towels to soak up excess moisture. Salt and pepper both sides of the salmon.
Heat a cast iron over medium-high heat. Add avocado oil until shimmering. Sear salmon skin side down. Lay dill and lemon on top of the salmon placing the half of the lemon somewhere on the pan. Sear for 2-3 minutes until salmon skin is brown.
Drop 2 tablespoon of butter into the pan with crushed garlic. Baste the salmon with the butter until it is mostly gone about 1 minute. Transfer the entire cast iron pan to the oven. Cook for 3-7 more minutes or until salmon reaches exactly 120° for a medium rare salmon. Squeeze the half of the lemon over the fish. Remove from cast iron pan immediately.
Serve with Jasmine rice and roasted aspargus.
Notes
Rinse the salmon to remove any ice crystals that remain on it. Use a paper towel to apply pressure to the salmon, without pushing too hard, to remove as much liquid as possible. Do this to both sides of the fish.
Removing excess water from frozen salmon makes the fish cook evenly and will make sure that it doesn't get cooked by steam as that moisture heats up.