Spinach Squares

Ingredients

• 1 cup flour
• 1 teaspoon salt
• 1 teaspoon baking powder
• 1 cup milk
• 1/2 cup melted butter
• 1/2 cup finely chopped onion
• 1 lb grated sharp cheddar cheese
• 2 eggs
• 1 (10 ounce) frozen chopped spinach (drain, thaw)