Preheat oven to 450°. Heat 1 1/2 tablespoons oil in a nonstick skillet over medium-high heat. Add onion and 1/8 teaspoon salt; sauté 8 minutes or until onions are lightly caramelized. Transfer to a small bowl.
Brush flatbreads with remaining 1 1/2 teaspoons oil. Stir together ricotta, garlic, and remaining 1/8 teaspoon salt in a small mixing bowl, and spread onto flatbreads. Top evenly with cheeses and caramelized onion. Sprinkle with sesame seeds.
Place flatbreads on a large baking sheet, and bake 12 minutes or until cheese is melted and flatbreads are crisp. Let stand 5 minutes. Sprinkle with basil and orange zest, and cut into slices.
Sip: Domaine de Baumard Cremant de Loire "Carte Turquoise," NV, 50% Chenin Blanc, 50% Cabernet Franc ($21): "The presence of green apple and golden raspberry pairs incredibly well with the mix of cheeses and black sesame. Add the light acidity from this sparkling wine and it is a great match." --Michael Velo, bubbly expert from the Carriage House Restaurant in Chicago