1) Into a microwavable dish, add in cooking oil, onions. Cover and cook the onions for about 3 minutes.
2) Add in the cornflour. Stir well.
3) Stir in the curry paste, canned tomatoes with juice, bouillon stock, lemon juice, sugar, salt and pepper.
4) Cover again and cook for 6 minutes this time. Stir the mixture twice in between.
5) Serve the Curry Sauce with cooked meat, poultry or fish. You may even serve it over steamed rice.