Preheat oven to 450 degrees F and lightly brush 2 shallow baking pans or sheet pans with oil. Cut tomatoes into 1/2-inch thick slices and arrange in 1 layer in baking pans. Roast tomatoes in upper and lower thirds of oven until just tender but not falling apart, about 15 minutes, and cool slightly in pans on racks. Leave oven on.
Halve garlic. Cut bread into 1/2-inch thick slices and with a 4-inch round cutter cut out 4 rounds. Brush rounds on both sides with remaining 1/3 cup oil and arrange in 1 layer on a baking sheet. Toast rounds in middle of oven until golden brown, about 5 minutes, and immediately rub on both sides with cut sides of garlic. Season toasted rounds with salt and pepper.
Brush the bottoms and sides of 4 (4-inch diameter, 1 cup measurement) ramekins lightly with extra-virgin olive oil.
Layer 1 slice each of yellow and red tomato in bottom of each ramekin and spread 1 teaspoon pesto evenly over each. Repeat layering once and top each tatin with a toast round. Bake tatins in middle of oven just until hot, about 5 minutes. Invert a plate over each ramekin and invert ramekins onto plates.
Serve tatins immediately.
Recipe courtesy of Gourmet Magazine