1 1/2 cups small to medium fresh basil leaves, divided
2/3 cup plus 2 tablespoons extra-virgin olive oil, divided
1 large shallot, thinly sliced
1 small Fresno chile or red jalapeño, seeded, finely chopped
2 teaspoons finely grated lemon zest
2 tablespoons fresh lemon juice
Kosher salt and freshly ground black pepper
3 pounds ripe tomatoes, assorted colors and sizes
1 12-ounce loaf rustic or sourdough bread, cut into 1/2′-thick slices
1 pinch garlic clove, halved
Purée 3/4 cup basil leaves and 1/3 cup plus 2 tablespoons oil in a blender until smooth and only tiny flecks of basil remain. Set a fine-mesh strainer over a large bowl. Strain mixture into bowl, pressing on solids to extract as much oil as possible; discard solids in strainer. Add shallot, chile, lemon zest, and lemon juice to basil oil; whisk to blend. Season to taste with salt and pepper. DO AHEAD Dressing can be made 1 day ahead. Cover and chill. Return to room temperature and rewhisk before using.
Slice tomatoes into assorted wedges, rounds, and cubes; add to bowl with dressing. Toss to coat; let marinate at room temperature for 30 minutes.
Meanwhile, build a medium-hot fire in a charcoal grill, or preheat a gas grill to high. Brush bread with remaining 1/3 cup olive oil. Season with salt and pepper. Grill bread until charred in spots, about 2 minutes per side. Rub grilled bread with cut sides of garlic clove. Tear bread into 1″-2″ pieces.
Add bread and remaining 3/4 cup basil leaves to bowl with tomato mixture; toss to coat. Season panzanella to taste with salt and pepper and serve.