Could it be true? Dropping temperatures in late August, reminding us that summer won’t last forever. The perfect day for a caramelized onion tart for a late breakfast. This is sweet and savory all at once, the bacon and fennel coming together perfectly on the bed of caramelized onions.
- About a cup of very active sourdough starter. If you haven’t got sourdough at hand, substitute commercial yeast.
- 1/2 cup hand-warm water
- 1 1/2 to 1 3/4 cups all-purpose white flour
- 1 large egg
- Some good olive oil
- A good pinch of dalt
- Fennel seeds, about a tablespoon full
- 3 pound red or yellow onions, thinly sliced
- 1 tablespoon Dijon mustard
- Grated Parmigiano, as much as you like.
- A good handful of diced bacon
Put 1 1/2 cups flour in a bowl and the add the sourdough starter. Add the egg, 1 tablespoon oil, and 1 1/2 teaspoons salt. Mix, gradually incorporating flour, until a soft dough forms. Then knead, I use a Kitchen Aid for this, adding additional flour as needed, until smooth and elastic. Transfer dough to an oiled bowl and coat with a little more oil. Cover and let rise in a draft-free place until doubled, 2 to 3 hours.
While dough rises, gently heat some olive oil in a cast iron skillet over medium-high heat until it shimmers, then sauté the fennel seeds until a shade darker, about 30 seconds. Stir in the onions, salt and pepper, then reduce heat to low and cover. Cook, stirring occasionally, until onions are very tender and golden brown, 1 to 1 1/4 hours.
Preheat oven to 375°F with rack in middle.
Knead dough gently on a floured surface with floured hands to deflate. Pat out dough on a large heavy baking sheet into a 15- by 12-inch rectangle, turning up or crimping edge, then brush mustard evenly over dough, leaving a 1/2-inch border around edge. Spread onions evenly over mustard, then sprinkle evenly with cheese. Add the bacon dice.
Bake tart until crust is golden brown and the bacon cooked, 30 to 35 minutes. Serve warm or at room temperature.