In a large, non-stick skillet over medium - high heat, melt one tablespoon of the butter. Add the shaved steak and cook, stirring often, until no longer pink. Remove the steak from the pan, leaving behind the juices.
Over medium heat, add the remaining tablespoon of butter and melt. Add the garlic and cook, stirring often, until fragrant, about one minute.
Add the tomato paste, chili powder, sugar, smoked paprika, red pepper flakes and salt. Cook, stirring often, for an additional minute.
Stir in the beer and cook for a couple of minutes until smooth. Return the steak to the pan with the sauce and stir to combine and cook for a few minutes until heated through.
Serve the steak with tortillas and toppings to make tacos.