This one is straight-forward and should do what you want:-
2 tablespoons vegetable oil
1 onion, finely chopped
1 garlic clove, finely chopped
1 lemon
1/2 cup/100 g brown sugar
1/4 cup/60 ml vinegar
1/2 cup/125 ml tomato ketchup
1 tablespoon Worcestershire sauce
1/2 teaspoon Tabasco sauce, or to taste
1/4 teaspoon chili powder, or to taste
Heat the oil in a frying pan and sauté the onion and garlic until soft and lightly browned, 4-5 minutes. Grate the zest from the lemon and squeeze the juice. Add the lemon zest, half the lemon juice, the sugar, vinegar, ketchup, Worcestershire sauce, Tabasco sauce and chili powder to the onion and simmer gently, 5 minutes. Taste, adjust the seasoning and let cool.
Light the grill. Season the pork with salt and pepper and brush with the cooled barbecue sauce. Grill them, basting often, 5-7 minutes. Turn over and continue grilling and basting until the meat is done, (5-7 minutes longer).