Heat the oven to 425įF.
Make the spice rub:
In a small skillet, heat the coriander seeds over medium heat, stirring frequently, until they are lightly golden brown and aromatic, about 3 minutes. Remove from the heat and let cool slightly.
Grind the seeds in an electric grinder and transfer to a small bowl. Use your fingers to stir in the sumac or paprika, lemon zest, and salt.
Make the fish and fennel:
Quarter the fennel bulb, core, and slice it lengthwise about 3/16 inch thick, to yield 1-1/2 cups. Save about 1/2 cup fronds for garnish.
Generously coat the salmon fillets on all sides with the rub and set the fillets on a plate. In a small bowl, stir together 4 tsp. of the lemon juice and the honey.
In a heavy 12-inch ovenproof skillet, heat 3 tablespoons of the oil over medium-high heat. When the oil is shimmering hot, arrange the salmon fillets evenly in the pan, skinned side up. Add the fennel to the pan, fitting it into the spaces around the fish. (It will look like thereís not much room, but you will be able to squeeze this amount of fennel around the fillets.)
Sear for about 2 minutes, without moving; then use a slotted metal spatula to lift a piece of fish and check the color. When the fillets are nicely browned, flip them and put the pan in the oven.
Roast until the salmon is barely cooked in the center, 4 to 6 minutes. While the salmon is roasting, toss the fennel fronds in a medium bowl with the remaining 1 teaspoon olive oil.
Core the apple half and cut it into matchsticks. Add to the fennel fronds. Sprinkle the remaining 1/2 teaspoon lemon juice over the apples, season with salt and pepper, and toss again.
When the salmon is cooked, remove the pan from the oven and transfer the salmon with the spatula to serving plates.
Taste the fennel; if it is still crunchy, set the pan over medium heat and cook the fennel a few minutes more, stirring occasionally, until itís tender. With the spatula, transfer the fennel to a small plate.
Pour off and discard any oil in the pan, blotting the pan with a wad of paper towels (there will be some browned spice rub sticking to the pan, which is fine). Return the pan to the stove over medium-high heat and add the lemon-honey mixture.
Bring to a boil, stirring with a whisk or wooden spoon to release the browned bits. Add the cooked fennel and stir to coat it with the glaze. Remove the pan from the heat. Season to taste with salt and pepper.
Top each piece of salmon with some of the glazed fennel and then a little mound of apple salad. If any glaze remains in the pan, drizzle some around each piece of salmon. Sprinkle each portion with a good pinch of fennel pollen, and serve immediately.