Preheat oven to 350 degrees Fahrenheit.

Heat olive oil in a large non-stick skillet over medium heat.

Add sliced onions, minced garlic, and bay leaf to the skillet.

Saute the onion mixture for approximately 25 minutes, until the onions turn a deep golden color.

Remove the skillet from heat and allow the onion mixture to cool slightly.

Discard the bay leaf from the cooled onion mixture.

Puree the caramelized onion mixture in a blender until smooth.

Position an oven rack in the center of the oven.

Line a baking sheet or cookie sheet with parchment paper.

In a large mixing bowl, sift together the unbleached white flour, sugar, baking soda, cream of tartar, and salt.

Stir in the lightly crushed caraway seeds.

Create a well in the center of the flour mixture.

In a small bowl, whisk together the buttermilk and plain yogurt.

Add the buttermilk-yogurt mixture and the pureed onions to the flour well.

Stir the ingredients together until just mixed. Avoid overstirring.

Turn the dough out onto a lightly floured board.

Knead the dough until it becomes smooth, about 2 minutes.

Shape the dough into a round, approximately 6 inches in diameter and 2 1/2 inches high.

Place the shaped dough onto the prepared baking sheet.

If desired, use a sharp knife to cut a deep cross design in the top center of the dough.

Dust the top of the dough with a light dusting of flour.

Bake the bread for approximately 55 minutes, or until the outside is light brown and crusty.

Check for doneness by tapping the top of the loaf; it should sound hollow when thoroughly baked.

Transfer the baked bread to a wire rack to cool completely before slicing and serving.