Pour beer and water into a large stock pot. Add salt and stir to dissolve. Bring mixture to a boil over medium high heat.
In a large frypan or frying pan, heat vegetable oil over high heat. Sear ribs on both sides. Place on paper towels to briefly drain. Add seared ribs to the beer/water mixture. Add more water as needed to cover the ribs. Cover pot and simmer for 2 hours.
While the ribs are simmering, melt the butter in a sauce pan and saute the onions and garlic until onions are translucent. Stir in tomatoes, tomato sauce, molasses, Worcestershire, mustard, salt, Tabasco sauce and vinegar. Bring to a slow boil, stirring constantly. Reduce heat to low and leave it simmering until the ribs are finished.
Preheat oven to 180 degrees C.
Drain ribs and arrange them in a shallow baking tray. Ladle the sauce over the ribs evenly, slice each slice of lemon in half, and distribute the half slices on top of the sauce. Cover with foil loosely and place in the oven for 15 minutes then uncover for the last 10, a total of 25 minutes oven time. Remove rind from lemon slices, discard rind, returning lemon "meat" to sauce on top of the ribs, and serve ribs covering each with sauce on the plate.