Rinse and pat dry the heirloom tomatoes. Slice each tomato into 1/4-inch to 1/2-inch thick rounds. If using large tomatoes, cut into 1/4-inch slices; if smaller, cut into halves or thick slices as appropriate. Drain mozzarella and slice into rounds roughly the same thickness as the tomatoes (or tear bocconcini into similar-sized pieces).

Arrange

On a large platter or individual plates, alternate tomato and mozzarella slices in an overlapping pattern (tomato, mozzarella, basil leaf, repeat) around the plate. Tuck whole or torn basil leaves between slices for even distribution.

Season

Lightly sprinkle flaky sea salt and freshly ground black pepper evenly over the arranged salad.

Pesto Oil

Make pesto oil

In a small blender or food processor combine 1 cup fresh basil, 1 garlic clove, 1 tbsp toasted pine nuts, 2 tbsp grated Parmesan, 1 tsp lemon juice and 1/4 tsp salt. Pulse to a rough paste, scraping down the sides as needed. With the motor running, slowly pour in 1/2 cup extra-virgin olive oil until emulsified and smooth but still pourable. Taste and adjust salt or lemon as desired. If the mixture is too thick, add a teaspoon or two more olive oil.

Strain (optional)

For a brighter green finish, you may strain the pesto oil through a fine mesh sieve into a bowl, pressing solids with the back of a spoon; otherwise use as-is for more texture.

Balsamic Glaze

Reduce balsamic

In a small saucepan combine 1/2 cup black balsamic vinegar and 1 tbsp brown sugar or honey. Bring to a gentle simmer over medium-low heat, stirring until the sugar dissolves. Reduce heat to maintain a very gentle simmer and cook until mixture thickens to a syrupy consistency that coats the back of a spoon, about 8–12 minutes. Watch closely to avoid burning. The glaze will continue to thicken as it cools.

Cool

Remove from heat and let the glaze cool to room temperature. Transfer to a squeeze bottle or small bowl for drizzling.

Finish

Dress and serve

Drizzle about 1 tablespoon extra-virgin olive oil lightly over the arranged salad, then drizzle 2–3 tablespoons of the pesto oil over the top in a decorative pattern. Finish by drizzling 1–2 tablespoons of the black balsamic glaze across the salad. Taste and add any additional flaky salt or pepper to taste. Serve immediately.