Instructions

1. Pour beer into into a gallon-sized sealable plastic bag, or dish large enough to accommodate meat. Stir in garlic and place beef, meaty side down, into marinade. Marinate at least 12 hours and up to 24 hours refrigerated.
2. Remove brisket from marinade, do NOT discard marinade.
3. Make a rub by combining salt, 1 tablespoon of the sugar and dry rub. Score fatty side of brisket with a cross-hatch, 1/8-inch deep, then liberally rub mixture all over meat. Allow meat to come to room temperature.
4. Preheat oven to 250 degrees. Bake, uncovered, fat side up, on roasting rack on center rack of oven 3 hours.
5. While meat is cooking, add remaining sugar to the reserved beer marinade mixture. Reduce in saucepan, skimming scum from top, until slightly syrupy; until mixture is about 1/3 cup.
6. Remove meat from oven, baste top with mixture, turn beef over, baste again, cover or enclose top with foil and return to oven for an additional 1 1/2 hours.
7. Prepare grill to low heat. Remove brisket from oven, place on grill.
8. While brisket is grilling, place onion slices and whole peppers on grill. Grill onions alongside beef until tender. If possible, raise heat over poblanos to high and grill until charred on all sides. Place peppers in a paper or plastic bag. When cool enough to handle, remove top and seeds, and pull off charred skin with your fingers. Cut into slices.
9. Grill beef until internal temperature reaches 197 degrees, then remove from heat, wrap in foil and let rest 15 minutes before slicing into strips against the grain.
10. Before serving, place the tortillas on the grill and sprinkle with cheese. When the cheese has just begun to melt, stuff with sliced brisket, onions and peppers, fold over to make a taco and serve with salsa.