Traditionally served as tapas (an appetizer) in Spanish restaurants and bars, this version of the Spanish tortilla removes a lot of the fat and makes a healthy breakfast casserole. Conventionally it does not contain cheese, but feel free to sprinkle some on top in the last 30 minutes of cooking.
2 small onions, finely diced
3 tbsp olive oil
10 large eggs
1 tsp salt
1 tsp ground pepper
3 large baking potatoes, peeled and thinly sliced
In a skillet over medium heat, slowly cook onions in olive oil until lightly brown and caramelized, about 5–6 minutes.
In a large bowl whisk together the eggs, salt, and pepper.
Layer half of the potatoes and fried onions in a greased 4-quart slow cooker. Pour half the eggs over the layers. Repeat layers ending with the last of the whisked eggs.
Cover and cook on low for 6–7 hours or on high for 3½–4 hours.