Preheat your oven to 350°F (175°C) and position the rack in the center.

Prepare a 9-10 inch springform pan by laying a piece of parchment paper over the bottom. Snap the ring over it to hold the parchment in place, then trim any excess paper hanging over the edges. Grease the bottom and sides of the pan with vegetable shortening or butter.

In a large sauté pan, heat 2 tablespoons of olive oil over medium-high heat. Add the ground beef and sausage, cooking until browned. Drain the meat in a strainer, reserving the liquid. Let the fat rise to the top, then skim it off and set the liquid aside.

In the same pan, add the remaining tablespoon of olive oil over medium heat. Add the diced onions, bell peppers, basil, oregano, salt, black pepper, and red pepper flakes. Sauté for about 4 minutes until the vegetables are tender but still firm.

Stir in the minced garlic and cook for an additional minute. Create a space in the center of the pan, add the tomato paste, and cook for 1 minute. Mix in 2 tablespoons of the reserved meat liquid and return the cooked meat to the pan. Stir to combine and set aside.

In a medium bowl, whisk together the eggs, Greek yogurt, salt, baking powder, and flour until smooth. The batter should be similar to pancake batter.

Pour half of the batter into the prepared springform pan, spreading it evenly to the edges. Layer half of the cooked meat mixture on top, spreading it out as well.

Sprinkle the grated Parmesan cheese over the meat, then layer the provolone cheese slices on top, overlapping them slightly.

Add the remaining meat mixture on top of the provolone, spreading it evenly. Mix the scallions and mozzarella into the remaining batter, then pour this mixture over the top, spreading it to the edges.

Cover a medium baking sheet with foil and place the springform pan in the center to catch any drips. Bake for 45 minutes. If the top needs browning, broil for an additional 2 minutes.

Allow the bake to sit for 10 minutes in the pan. Gently press the center; it should feel firm like a quiche. If it feels soft, let it sit for another 5 minutes.