Satellite dishes are designed to create a focal point of energy, which makes them ideal to create a cooker as the sun's rays can be concentrated to create a great amount of heat, the amount of heat depends on the size of the dish.
The size viewed in these videos can boil a liter of water in about 10 min.
Here we have 2 videos on creating a parabolic solar cooker from satellite dishes. Each have good tips so take what you want.
Don't have a satellite dish? Got instructions on making a parabolic solar cooker from cardboard.