Impossible Tuna Cheese Pie

• 3 eggs
• 2 onions (chopped)
• 2 cans tuna (drained)
• 1 biscuick
• 300 ml milk
• 230 gr cheddar cheese (shredded)
• 55 gr butter
• 1 gr salt if desired
• 1 gr pepper
• 2 slices tomatoes thinly (sliced)