Appetizer Flatbreads with Goat Cheese, Caramelized Onions, and Basil

olive oil, plus more for brushing on the bread

yellow onions, sliced into 1/4-inch half moons

salt

Freshly ground pepper

sugar (optional)

flatbreads

goat cheese

to 10 large fresh basil leaves, cut into chiffonade

to 10

crunchy sea salt, such as Maldon

(4.3%)