Heat Vegetable Oil (2 tablespoon) in a medium-size skillet, add Onion (2 cup) and Kosher Salt (1/2 teaspoon), cook until onions are starting to soften.
Add the Spanish Chorizo (7 ounce) and Dried Oregano (1 teaspoon), 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 degrees F (175 degrees C).
In a small bowl, whisk together All-Purpose Flour (1 1/4 cup), Baking Powder (2 teaspoon), Kosher Salt (1/2 teaspoon), Garlic Powder (1/2 teaspoon), Ground Black Pepper (1/2 teaspoon), and Onion Powder (1/2 teaspoon).
In a large bowl, whisk together Egg (5) and Vegetable Oil (1/2 cup). Add Sour Cream (1/3 cup) and whisk until smooth. Add Frozen Spinach (6 ounce) and stir to combine.
Add dry ingredients to wet all at once. Whisk until combined, but do not over mix. Stir in onions, chorizo and Cheddar Cheese (6 ounce).
Spread evenly onto a parchment lined 15x10-inch baking sheet. 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 by loosening the edge, grabbing a corner of parchment and pulling the entire piece onto the board. Cut into 16 squares and serve immediately, enjoy!