Three Onion Quiche

This recipe came with a shipment from the "Sunset Wine Club".  For what it's worth, they suggest pairing with "Cachette NV Blanc de Blancs Brut" from Burgundy, France.  We had it for breakfast with a glass of milk and it was great.

1 sheet refrigerated pie dough
1 tablespoon butter
3 medium leeks, thinly slice the white and light green parts, rinse well
2 bunches green onions, thickly sliced
1/2 red onion, cut into thin half-moons
1 teaspoon salt
1 tablespoon flour
1 cup half-and-half
3 eggs
2 cups grated white cheddar cheese

Preheat the oven to 425°.  Unroll pie dough into a 9-inch deep dish pie pan, crimp the edge.  Line with parchment paper and fill with pie weights (or dried beans, popcorn, or something to add weight on the crust).  Bake until light golden, about 15 minutes.  Remove paper and weights.

Melt butter in a large frying pan over medium heat.  Add leeks, green onions, red onion, and 1/2 of the salt.  Saute until onions are very tender, about 20 minutes.

Whisk together the half-and-half, flour, eggs, and remaining salt.  Stir in the cheese and 3/4 of the onion mixture.  Pour into the pie shell.  Sprinkle the remaining onion mixture on top.

Bake until a knife inserted in the center comes clean, 30-45 minutes.  Cover edges with foil if they get dark.  Let cool about 10 minutes before serving.