My mom used to make this as I was growing up. I recently found it and have put it into our weekly rotation. You can also substitute a can of chicken. I put it serves 4 because our family always goes back for seconds.
Preheat oven to 350 degrees F (175 degrees C).
Place eggs in a saucepan and cover with cold water. Bring water to a boil. Cover pan, remove from heat, and let eggs stand in the hot water for 10 to 12 minutes. Remove from water; peel and chop.
Combine the chopped eggs, spinach, onion powder, tuna, cream of mushroom soup, and sour cream in a 9x13 inch baking dish. Mix well. Scatter bread pieces over tuna mix; drizzle with melted butter.
Bake in preheated oven until bread is toasted and casserole is hot, about 30 to 35 minutes.
Per Serving: 339 calories; protein 21.3g; carbohydrates 17.3g; fat 21.2g; cholesterol 180mg; sodium 760mg.