Place sesame seeds in a shallow bowl. Rub salmon fillets with 2 tsp. oil and sprinkle with salt and pepper. Press flesh side of fillets in sesame seeds to coat.
Warm remaining 1 Tbsp. oil in a large nonstick skillet over high heat until shimmering, 2 to 3 minutes. Place salmon fillets, skin side down, in skillet; reduce heat to medium-high and cook until skin is browned and bottom halves of fillets are opaque, about 4 minutes. Turn and cook until fish is done, about 3 minutes for medium-rare. Transfer fish to plates, flipping fillets so seed side is up; serve immediately.