dissolve yeast with sugar in 1/2 cup warm water. set aside for 10 minutes until mixture bubbles. sift flour and salt into large mixing bowl. make well in center and pour oil and yeast mixture. mix vigourously. add warm water slowly to make soft dough. knead for 15 minutes and starts to come away from sides of bowl. cover bowl with cloth and set in warm dry place for 2-3 hours until double in size.
saute onion in oil briefly. mix meat, tomatoes and tomato paste in bowl. add sugar, allspice and lemon juice. season with salt and pepper and add cooked onion, parsley and cayenne. knead well. roll out dough on pizza pan. spread meat mixture on top. add cheese if desired, and bake at 475 degrees for 10 minutes.