Cook 1 ounce thinly sliced pancetta in a medium skillet over medium heat, stirring occasionally, until crisp, about 5 minutes. Let cool on paper towels; crumble. Bring 1 tablespoon sugar and 2 tablespoons water to a boil in same skillet, stirring to dissolve sugar. Add 2 cups halved red seedless grapes, 1 teaspoon coarsely ground black pepper, and 1/4 teaspoon crushed red pepper flakes. Cook until grapes are glazed and start to soften, about 5 minutes. Mix in pancetta; season with salt. Spread 4 toasted slices of bread with 1/2 cup ricotta. Top with grape mixture and chopped tarragon and drizzle with olive oil.
