Vegetarian "BLT" Sandwich

Ingredients (8)

• 4 large or 6 medium slices of sourdough bread
• 2 medium-to-large ripe red tomatoes
• Flaky sea salt or kosher salt
• 6 ounces halloumi cheese
• ¼ cup extra-virgin olive oil, for frying
• Freshly ground black pepper
• 6 tablespoons mayonnaise, or as needed
• 6 tender green lettuce leaves (I like butter lettuce)