A simple tart where soft caramelized onions meet salty swiss cheese in a buttery, crisp shell. This is what you make when you have good cheese and want supper ready in forty minutes, no yeast required.

Serves 2. 45 minutes, 20 at the stove.

About 850 calories a serving, 27 g protein, 60 g carbohydrate, 56 g fat. From USDA figures for 100% of the ingredients; amounts are the recipe's.

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1. Mix 1 cup flour, 4 tablespoons cold butter cut into cubes, 1/4 teaspoon salt, and 3 tablespoons cold water with your fingertips until the dough looks like coarse breadcrumbs, then gather into a ball and chill while you work.
2. Slice 2 medium onions into thin half-moons and warm 2 tablespoons oil in a large skillet over medium heat. Cook the onions for 12 to 15 minutes, stirring often, until they turn soft and golden at the edges, then taste and season with salt and pepper.12 min
3. Heat the oven to 400°F [200°C]. Roll the dough thin between two sheets of parchment, lay it on a baking sheet, and prick it all over with a fork; bake for 10 minutes until just set but not colored.10 min
4. Whisk 1 egg with 2 tablespoons cold water and a pinch of salt. Spread the caramelized onions on the warm crust, scatter 4 oz swiss cheese shredded or torn into small pieces over the top, then pour the egg mixture evenly over all.
5. Bake for 12 to 15 minutes at 400°F [200°C] until the custard is just set and pale gold, then remove and let rest for 2 minutes before serving.13 min

Note Swap the swiss for gruyere or any melting cheese. Leftovers keep covered in the fridge for two days and reheat gently in a low oven. Serve with a green salad dressed with vinegar and oil, or with a sharp mustard on the side.