Onion and Rosemary Focaccia - National Onion Association

Ingredients

• 1 small russet potato
• 2-1/2 cups cold water
• 5 cups all-purpose flour
• 2-1/2 teaspoons active dry yeast
• 1 teaspoon sugar
• Kosher salt
• 2 tablespoons olive oil, plus more for oiling the pan
• 1 small sprig fresh rosemary
• 2 small sweet onions, thinly sliced
• 3 tablespoons olive oil
• 3/4 teaspoon flaky sea salt