6 cups cubed whole grain bread
1 1/2 pounds fresh asparagus, trimmed and cut into 1-inch pieces
1 1/2 cups chopped onion
3 cups fresh baby spinach
1 1/2 cups whole milk
1/2 teaspoon sea salt or kosher salt
1/2 teaspoon freshly ground black pepper
3 plum tomatoes, thinly sliced
3/4 cup feta cheese (maybe substitute chedder or other cheese)
1/3 cup snipped fresh basil
Coat 3 quart rectangular baking dish with oil. Arrange half of the bread cubes in the prepared baking dish.
In a covered medium saucepan, cook asparagus and onion in a small amount of boiling water for 2 to 3 minutes or just until tender; stir in spinach. Immediately drain well. Spoon half of the asparagus mixture over bread in baking dish. Top with the remaining bread cubes and the remaining asparagus mixture. Set aside.
In a large bowl, whisk together eggs, milk, salt, and pepper. Pour evenly over mixture in baking dish. With the back of a large spoon, lightly press down layers. Arrange tomato slices on top. Top with feta cheese and basil. Cover with foil; refrigerate for 4 to 24 hours.
Preheat oven to 325 degrees F. Bake, covered, for 30 minutes. Uncover; bake about 40 minutes more or until center registers 180 degrees F when tested with an instant-read thermometer (there will be some liquid left in center that will be absorbed during standing). Let stand on a wire rack for 10 minutes before bring to the potluck!