With the advent of frozen all-butter puff pastry available for the home cook, we can make many inventive dishes that are Seriously Simple. I’ve made my share of desserts with commercial puff pastry, but this is my first attempt at a first course or appetizer. I wanted to prepare a simple summer tart that was full of lively flavors. What could be better than tomatoes and pesto? Working with puff pastry takes a little getting used to. Make sure to defrost the pastry before you roll it out to desired size. I like using parchment paper sheets under the pastry for ease in rolling and also for transferring the pastry onto the sheet pan. Make sure to use a sharp knife to carve out the half-inch border, but don’t cut all the way through. I found that punching little holes inside the border with a fork close together helps keep …