In a small bowl add dry yeast to the lukewarm water. Mix and rest for 5 minutes.
Add flour, salt, and sugar in a large bowl. Add cubed butter to the outside of the bowl. Make a well in the center and pour the yeast water into the center.
Use the dough hook of your electric mixer (or your hands) and knead the dough until well combined. Shape into dough ball. Cover bowl with a dish towel. Rest dough at room temperature for 30 minutes..
Use a rolling pin and roll the dough on a flour-dusted surface. Roll until the dough exceeds the size of your baking sheet by approximately ¼ inch. Transfer dough onto baking sheet. Press dough up the edges of the baking sheet. Cut off any excess dough. Set aside
Use a large frying pan and heat olive oil over medium-high heat. Add bacon and allow to crisp. Add onion and sauté until softened.
In a medium bowl, whisk eggs, heavy cream, nutmeg, and salt with an electric mixer (whisk attachment) for 1 minute.
Remove the softened onions and bacon from the heat. Pour egg mixture into the frying pan and combine well.
Pour the onion and egg mixture onto the dough-covered baking sheet. Sprinkle with grated cheese.
Bake at 400° Fahrenheit for 30 minutes.
STORE AND KEEP
REFRIGERATE: Store the Onion Pie in the fridge for 3-4 days. FREEZE: Let the Onion Pie cool completely. Cut the pie into portion-sized rectangles. Wrap with plastic wrap and store in a ziplock back or a freezer-friendly container.