TO SERVE
Heat oil in a large skillet over medium-high heat until shimmering. Add onions and peppers and cook, stirring frequently, until softened and well-browned, about 10 minutes.
Add chorizo and cook, breaking it up as it browns. Continue cook until meat is cooked through, abut 5 minutes.
Drain excess fat and return pan to heat. Add sugar and tomato sauce and cook, stirring, until reduced to a sauce-like texture. Stir in hot sauce and season to taste with salt and pepper.
Toast buns. Spoon mixture into burger buns, top with avocado and onion, and serve.