These six-ingredient bite-size appetizers taste best warm, so assemble them in advance and pop them in the oven when guests arrive.
Preheat oven to 350°. Scoop out some of the flesh from the center of each zucchini slice with a melon baller to create a bowl-shape shell. Place slices on a baking sheet lined with foil or parchment paper. Fill each shell with a crumble or two of blue cheese. Top with a tomato slice and a sprinkle of Parmesan cheese and pepper.
Bake for 5 to 7 minutes or until cheese melts. (Watch carefully so they do not brown.) Garnish with fresh basil leaves.