Cook the pasta in salted, boiling salted water until al dente. Drain in a colander.
Add the cherry tomatoes to a sheet tray, drizzle with olive oil and season with salt and pepper. Bake for 20 minutes, until visibly plump and softened.
Heat a large skillet over medium heat. Add 2 teaspoons of olive oil. Saute the chorizo in a saute pan until crisp. Remove. Melt 6 tablespoons butter in a large saucepot over medium heat. Add flour, stirring for 1 minute. Whisk in the warmed milk and bring to a boil. Continue to whisk constantly. Stir while adding the mustard, hot sauce and Worcestershire. Stir in the cheese; reserving 1/2 cup for the topping. The mixture will thicken as the heat increases.
Pour the drained pasta into the cheese sauce and mix well. Add to a 3-quart casserole dish. Add the chorizo and roasted cherry tomatoes. Top with reserved cheese and the fried onions. Bake for 35 minutes. Can be made ahead, covered and refrigerated. Bring to room temperature before baking if refrigerated.