Spray 4 large ovenproof ramekins (10cm) with olive oil. Microwave the tortillas for a few seconds to soften them and then carefully line the ramekins with the tortillas. Bake in the oven for about 7-10 minutes until they start to crisp up, then remove from the oven.
While the tortilla cases are baking. Pour boiling water over the spinach to wilt it, drain immediately, roughly chop and set aside.
In a large bowl mix the eggs, cherry tomatoes, crumbled Fetta and chopped blanched spinach. Season with salt and pepper. Divide the Fetta and egg mix between the tortillas, cover with foil and bake for 20-25 minutes or until the eggs are cooked through. Serve warm for breakfast or brunch.