Cheesy Spinach Squares

Preheat oven to 350 degrees F (175 degrees C). Grease one 9x13-inch baking dish.

Bring a large pot of water to a boil and add spinach. Cover reduce heat and cook until heated through 5 to 6 minutes. Drain well squeezing out excess moisture with your hands. Set aside to cool.

Melt butter in a saucepan over medium heat; stir in onion and cook until soft and translucent 5 to 10 minutes.

Transfer onions to a double boiler; mix in milk Cheddar cheese flour and ground black pepper; cook and stir until blended and smooth about 5 minutes. Remove from heat; fold in eggs and spinach. Pour the spinach mixture into baking dish and smooth top.

Bake uncovered in the preheated oven until a toothpick inserted in the center comes out clean about 30 minutes. Cool briefly before cutting into squares.