Preheat the oven to 350. Place a sheet of parchment paper in a glass or ceramic baking dish that will hold the peppers snugly.
Place the peppers skin side down in the dish and put 2 tsp of pesto in each. Divide the cherry tomatoes among the 6 halves. Drizzle with olive oil and season with salt and black pepper. Roast for 30 minutes
Just before serving, add the mozzarella pearls and a little more olive oil if needed and pop back into the oven until the cheese melts.
Garnish with sliced fresh basil leaves and serve immediately.