Preheat oven to 400°F. If the salmon fillets are very thin, you can cook them on the stove top.
Rinse salmon and pat dry. Remove pin bones if they have not already been removed.
Crush the fennel seeds, using either a mortar and pestle, a bag with a zipper closure and a rolling pin, or a mini grinder.
Brush the fillets with olive oil, sprinkle with salt and pepper.
Coat the fillets with crushed fennel seeds, pressing down gently to help them adhere.
In an ovenproof skillet, heat the oil over medium-high heat. Add the salmon, with the fennel mix side down (skin-side up) and heat for 3 to 5 minutes, depending on the thickness of the fillets.
Flip the fillets over and finish cooking in the oven for another 2 - 4 minutes or less, depending on the thickness of the fillets, until the fish flakes easily with a fork. The fish should be a little translucent in the thickest part.
Remove from the oven and let stand for 5 minutes. Slip the skin off before serving, if desired.
If the salmon fillets are thin, you may not need to finish baking them in the oven. Sear for 3 - 5 minutes skin side up, then turn and sear for 2-3 minutes on the other side. Time will depend on thickness of the fillets you are using.