Heat a large skillet or sauté pan over medium heat. Add andouille sausage and brown on both sides. Remove from pan and set aside.

Add butter to the pan and scrape bottom of the pan to release the browned bits (fond) from the pan. Sprinkle flour into pan and stir to combine.

Cook roux (butter and flour mixture) for 5 minutes, stirring occasionally.

Cook pasta according to package directions. Save at least 1/2 cup pasta water before draining.

Add onions and celery to the pan with butter and flour, season with salt and pepper. Cook for 5 - 6 minutes to soften. (Reduce heat if onions/celery start to brown)

Add tomatoes, garlic and hot sauce to celery and onions. Stir to combine. Reduce heat to medium low.

Add stock and andouille sausage to the pan and stir to combine. Cover and simmer 10 minutes on medium low heat.

Add lemon juice and pasta water to the sauce to adjust consistency (you may want to add all of it or only some of it), then gently fold in langostinos.

Divide pasta evenly into shallow bowls, and spoon langostino andouille mixture on top.

Sprinkle sliced scallions over pasta and serve.