Step 1: 1. Heat 1 tablespoon olive oil in a medium-sized, deep frying pan and cook onion, peeled and finely sliced, for 10 minutes until soft.
Step 2: 2. Meanwhile, peel, halve and thickly slice baking potato, and boil for 10 minutes until tender. Drain and add to the onions in the pan.
Step 3: 3. Preheat the grill to medium. Lightly beat eggs until combined. Stir in ham, roughly chopped; tomatoes, chopped; Cheddar, grated; and fresh basil, roughly chopped. Season with salt and pepper and pour the mixture into the frying pan. Fry for 5-10 minutes on a low heat, gently moving the mixture around until it starts to set.
Step 4: 4. Once the frittata is set, but still a little wobbly on top, place under the grill until fully set. Allow the frittata to rest for a few minutes, then turn out onto a plate. Cut into wedges. Serve with salad if you wish.