I had something similar to this at a bar, so I thought I'd try to recreate it. You could also make this with larger tomatoes.
1 container fresh cherry tomatoes, rinsed
1/2 cup pesto, fresh or from a jar
1/2 cup shredded parmesan cheese
1/4 cup Italian style seasoned bread crumbs
1 tbsp olive oil
Salt and pepper, to taste
This is pretty simple! Use a paring knife to carve a circular hole in the top of the tomato. Fill with pesto, and then top with bread crumbs. Drizzle olive oil over the top of the bread crumbs - this will help hold the filling in. Next, sprinkle parmesan cheese over each tomato, then add salt and pepper.
Cook these in the oven at 350 until the cheese is melted and the tomatoes have begun to wrinkle (which means they are cooked!).
I've made these twice - the first time, on a baking sheet like above. The second time I used a mini-muffin pan, which made it a bit easier, as it stopped them from toppling over in the middle of the cooking process. Enjoy!