Simmer the sauce, (low heat) stirring until the sugar is melted. Then, stir occasionally for a few minutes while the oil is drawn out of the lemon. Do not allow to scorch.
1 32 oz. bottle ketchup
2/3 small jar prepared yellow mustard -- (i.e. French's)
1/2 pound dark brown sugar
1/3 large onion -- chopped coarsely
3 tablespoons distilled white vinegar
2 large lemons -- sliced
Tabasco hot sauce to taste
-- (3 drops to 1/2 tsp.
ground black pepper to taste