Heat the oven to 400°F (200°C).
Line a baking sheet with parchment paper or lightly oil a baking dish.
Pat the trout dry with paper towels. Removing extra moisture helps the fish roast instead of steam.
Season both sides with salt and pepper. Place the fillets skin-side down on the baking sheet or dish.
Make a quick drizzle: In a small bowl, mix olive oil, minced garlic, lemon zest, and a squeeze of lemon juice.
Stir in half the chopped dill. Spoon this over the trout.
Add lemon slices on top of each fillet. If using butter, dot small pieces around the fillets.
Sprinkle on capers and red pepper flakes if you like.
Bake for 10–12 minutes, depending on thickness. Thin fillets cook fast. You want the fish just opaque and starting to flake.
Optional finish: Switch the oven to broil for 1–2 minutes to lightly brown the edges.
Keep a close eye on it.
Rest and garnish: Let the trout rest for 2 minutes. Sprinkle with the remaining fresh dill and a bit of parsley. Add a final squeeze of lemon to brighten everything.
Serve with your favorite sides: roasted vegetables, steamed asparagus, rice pilaf, or a crisp green salad.