Preheat oven to 200 degrees C. Line a baking tray with non-stick baking paper.
In a small bowl, mix olive oil, cayenne pepper, salt, garlic powder and tofu together. Spread tofu out on the prepared tray. Bake for 15 minutes, shaking after five minutes.
Meanwhile, make sweet and sour sauce. In a small bowl, mix water and cornflour together to make a smooth paste.
In a small saucepan, over medium heat, mix vinegar, brown sugar, tomato sauce, pineapple juice and soy sauce together. Stire the mixture constantly with a wooden spoon until sugar dissolves and mixture boils.
Add cornflour and stir constantly until the mixture boils and thickens.
Serve sweet and sour sauce in a bowl with hot tofu.