Halve each cherry tomato, and place cut side up on a baking tray. Roast for around 20 minutes at 200°C (Gas Mark 6 / 400°F).
Meanwhile, scatter the grated cheese onto one of the slices of bread (if using). Put it under the grill (broiler) for a couple of minutes until melted.
Mash the avocado, and spread it onto the other slice of bread. Top with the roasted tomatoes (I like to let them cool a bit first), a good pinch of black pepper, a handful of salad greens, and a few ridge-cut crisps.
Put the two slices of bread together, and serve.