For the crust: Preheat the oven to 425 degrees F. Line a baking sheet with parchment.
In a bowl, mix together the hash browns, pepper jack, Cheddar, butter and eggs. Season with a good pinch of salt and pepper. Add the cayenne. Mix well.
Spray the parchment with cooking spray and add the hash brown mix. Shape into a large rectangle. Bake until the edges are golden brown, about 25 minutes.
For the toppings: Remove the hash brown crust from the oven. Top with the pepper jack, Cheddar, scallions and red and green bell peppers. Add the bacon, tearing it into pieces as you go. Return the pizza to the oven until the cheese is melted and the veggies are roasted, 12 to 14 minutes.
Using a pizza cutter, cut the pizza into slices and serve with salsa, sour cream, cilantro and sliced scallions.