In a skillet, cook the onion and green pepper in the olive oil until tender- about 5 mins. Add pineapple and let cook on medium-low. In a separate bowl, whisk the beer and pineapple juice together then stir in brown sugar, tomato paste, vinegar, chili sauce and cayenne pepper. Stir into the vegetable/pineapple mixture and let simmer til thickened a bit. Remove from heat, let stand for 5 mins and then process in a food processor or blender til as smooth as u like.