Glorious Tomatoes

I'm heading to the farmers' market in the morning to look for the early tomatoes and artisanal mozzarella. The big ones won't be ready yet, but some of the smaller varieties should be for sale. I want to make this for dinner tomorrow night:

Pomodoro Glorioso

2 cups canola oil, for frying
4 to 6 assorted heirloom tomatoes, sliced
1 teaspoon salt
1/2 teaspoon ground black pepper
1/2 cup Banyuls vinegar or white balsamic vinegar
2 medium to large balls fresh mozzarella, sliced
1 large Vidalia onion, very thinly sliced
1 cup buttermilk
1 cup all-purpose flour
6 fresh basil leaves, chiffonade
4 to 6 tablespoons basil oil

In a deep pot, preheat the oil to 375 degrees F.

On each of 4 to 6 appetizer plates, place 4 assorted slices of tomato, and season lightly with salt and freshly ground pepper. Drizzle 2 tablespoons of vinegar over each plate of tomato slices and then place 1 slice of mozzarella on each tomato slice.
Toss the onions in the buttermilk and drain. Dredge in the flour, shaking off any excess. Carefully drop the onions into the hot oil and fry until golden brown, around 2 minutes. Drain on paper towels and season with salt immediately. Top the cheese with the fried onions and chiffonade of basil. Drizzle a tablespoon of basil oil on each plate.