Summer-Veggie Melts with Caper Sauce

With the side of a heavy knife, mash garlic and 1/2 teaspoon salt to a paste. Transfer to a bowl and stir in mayonnaise, vinegar, capers, and basil.

Heat grill to high for both direct and indirect cooking. Drizzle bell peppers, onion, and Broccolini lightly with olive oil; season with salt and pepper. Brush grates with vegetable oil. Grill vegetables over direct heat, turning occasionally, until charred in places and crisp-tender, 8 to 9 minutes for peppers and onions; 4 to 5 minutes for Broccolini. Transfer to a plate; tent with foil.

Brush bread with olive oil and grill, cut-sides down, until lightly toasted, about 1 minute. Flip bread and move to indirect heat. Add cheese to one side, cover grill, and melt, 2 to 3 minutes. To serve, layer vegetables over melted cheese and spread other sides of bread with caper sauce. Cut each baguette in half to serve.