Fabienne's Cucumber Salad
1 lemon, juiced and zested 1 onion, diced 1 pinch salt, or as needed 2 cloves garlic, pressed 2 cucumbers - peeled, seeded, and diced 3 tablespoons low-fat Greek-style yogurt, or … 4 lettuce leaves 4 small tomatoes, quartered ¼ cup crushed pistachios, or to taste ⅛ teaspoon cayenne pepper ⅛ teaspoon ground black pepper