Line a sheet pan with aluminum foil to use as a holding vessel for the ribs.
In a mixing bowl, combine the mustard, meat spice blend, salt, sazón, curry powder, sugar, and red pepper flakes (if using).
Remove the ribs from the packaging and "wash" them with white distilled vinegar. Don't dry the ribs as the moisture will help the spice rub adhere to the ribs. Arrange the ribs on the prepared sheet pan.
Slather half of the spice rub on to one side of the racks of ribs. Flip them over and coat the other side with the remaining spice rub.
Stack the seasoned rib racks on top of one another and wrap them tightly in plastic film, then wrap them again in foil. This will contain any leaks that may occur while the ribs are marinating. Return the racks to the sheet pan and marinate the ribs in the refrigerator for 24 hours, or overnight.
Cook the Ribs
Preheat your oven to 250°F. Place an oven rack in the lower part of the oven.
Unwrap the ribs and arrange them, in a single layer, in a large roasting pan. Pour the ale or lager over the ribs and cover the pan, tightly, with aluminum foil.
Cook the ribs for 3 hours, or until their internal temperature reaches 190°F.
A half-hour before the ribs are due to come out of the oven, preheat a charcoal or gas grill to medium-high heat.
Transfer the ribs to the pre-heated grill and sear them for 5-6 minutes on each side. Remove them from the grill and allow them to rest for 15 minutes before cutting and enjoying.
These ribs can be marinated anywhere from 8 hours-3 days.