Spinach Frittata with Cherry Tomato and Cheddar

Ingredients

• 6 (2 oz or 60 g) whole eggs
• Kosher salt and freshly ground black pepper
• 2 tablespoons (1 fl oz or 30 ml) olive oil
• 1 medium (3.5 oz or 100 g) onion, chopped
• 1 cup (5 oz or 150 g) cherry tomatoes, halved
• 8 ounces (250 g) spinach leaves
• 2 ounces (60 g) cheddar, grated