Heirloom and Cherry Tomato Salad

Name: Heirloom and Cherry Tomato Salad
Ingredients: 1 medium shallot, finely diced (¼ cup); 2 Tbsp. red wine vinegar, plus more as needed; 1 medium garlic clove, finely minced (1 tsp.); Kosher salt; ½ cup extra-virgin olive oil; 1 cup mixed cherry and grape tomatoes, halved; 2 lb. mixed heirloom tomatoes, cored and cut into chunky 1-inch pieces or ½-inch slices; Freshly ground black pepper; Green and purple basil leaves, torn into small pieces; ½ cup thinly sliced lemon cucumbers or Persian cucumbers (optional); ½ cup thinly sliced torpedo onions or Vidalia onions (optional)