3/4 c cold butter
1 onion, finely chopped
1 T poppy seeds
kosher salt
freshly ground pepper
1 c coarsely shredded Gruyere cheese
2 c flour, plus more for dusting
2 t baking powder
1/2 t baking soda
1 t salt
1 c buttermilk
In a large skillet, melt 1/4 c butter; pour 2 T melted butter into a small bowl and reserve. Add onion to skillet and cook over moderate heat, stir occasionally, until softened, about 8 minutes. Stir in poppy seeds, salt and pepper. Scrape the onion mixture onto a plate and refrigerate for 5 minutes, until cooled slightly. Stir in Gruyere.
In a food processor, pulse flour, baking powder, baking soda and salt. Add 1/2 c cold cubed butter and pulse until the size of small peas. Add buttermilk and pulse 5 – 6 times, just until a soft dough forms.
Place dough onto a well floured work surface and knead 2 – 3 times. Pat dough into a 2 x 24-inch rectangle. Spread onion mixture on top. Cut dough crosswise into 10 pieces. Stack 9 pieces onion side up, top with final piece, onion side down. Carefully lay the stack in a buttered 9 x 4 1/2 inch loaf pan and brush with reserved butter.
Bake bread in center of oven at 425 degrees for 30 minutes, until golden. Let bread cool in pan for 15 minutes before removing from pan.
