Combine the flour and salt in a mixing bowl. Add the yeast, stir, add the warm water and mix again. Add 3 tablespoons of oil and knead the dough for 10 minutes until smooth. Place in a lightly oiled bowl, cover and let stand somewhere warm 45 minutes or until doubled in volume.
Saute the sliced onions in the remaining 3 tablespoons olive oil. Remove from the heat when browned. Toast the red capsicum under the grill until the skin is blackening, let cool, peel, and cut into strips.
Preheat oven to 220 degrees C. On a floured surface, roll out the pizza dough and put on a pizza tray. Spread with tomato pizza sauce, the onions and then the grated cheese. Arrange the strips of capsicum on top and sprinkle with mixed herbs. Bake 10 minutes or until edges of dough are brown.