Prep the oven and pan. Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper or foil for easy cleanup. You could also use a baking dish.
Season the fish. Pat the tilapia fillets really dry with paper towels. This is key for good texture! Place them on your prepared baking sheet. Sprinkle both sides generously with salt and freshly ground black pepper, then sprinkle the paprika, thyme, and oregano evenly over the fillets.
Make the buttery lemon sauce. In a small bowl, whisk together the melted butter, minced garlic, fresh lemon juice, and lemon zest.
Pour and top. Pour the glorious butter and lemon mixture evenly over each tilapia fillet. Arrange the lemon slices around or on top of the fish.
Bake! Pop the baking sheet into your preheated oven. Bake for 10-15 minutes, or until the fish is opaque and flakes easily with a fork. Thicker fillets will take a little longer. I usually check mine around the 10-minute mark.
Garnish and serve. Carefully remove the fish from the oven. Garnish with red pepper flakes (if using) and fresh chopped parsley. Serve immediately! It's delicious with rice, roasted vegetables, or a simple side salad.