Heat oil in a medium size skillet, add onions and 1/2 tsp kosher salt, cook until onions are starting to soften. Add chorizo and oregano, cook until onions have lost most of their moisture and are starting to caramelize. Remove from heat and allow to cool to room temperature.
Preheat oven to 350℉.
In a small bowl whisk together flour, baking powder, 1/2 tsp salt, garlic powder and onion powder.
In a large bowl whisk together eggs and oil. Add sour cream and spinach and stir to combine.
Add flour, baking powder, onion powder, garlic powder and salt and pepper. Whisk until combined, but do not over mix. Fold in onions, chorizo and cheddar cheese.
Spray a 15"x10" baking sheet with non-stick spray and line with parchment paper. Spread evenly onto tray and bake for 25-30 minutes until center is set.
Remove from oven and allow to cool for 5 minutes. Slide the entire cake onto a cutting board or cooling rack by loosening the edge, grabbing a corner of parchment and pulling the entire piece onto the board. Slide out parchment paper and cut into squares. Serve immediately.
Wrap two squares together with plastic wrap and store in a sealed container or zip lock bag in the freezer. Will keep frozen for up to two months. Rewarm thawed squares lightly in the microwave.