Preheat the oven to 400°F. Lightly spray a baking dish with cooking spray.

Season both sides of the tilapia fillets with salt and pepper, then place them in the dish.

In a small bowl, mix the pesto and sour cream. Spread the mixture evenly over the fillets.

Bake on the middle rack for 10–12 minutes, or until the fish flakes easily with a fork. Serve immediately.