Preheat oven to 350° F.
In a large pot, bring water to a boil. Cook penne pasta until al dente. Drain and set aside.
In a large pan, fully cook bacon on low to medium heat. Retain bacon grease in pan, and set cooked bacon aside to cool.
Add diced onion to the same pan. Sauté onion in bacon grease for 2-3 minutes. Add ground beef to pan. Break apart ground beef, and continue to stir until beef is cooked (approximately 5 minutes). Strain pan contents in a colander to remove excess grease. Return beef to pan.
Add spinach, pickle, and petite diced tomatoes to pan. Combine ingredients for 2 minutes on low heat. Strain mixture again in a colander to remove excess liquid. Then return mixture to pan.
Add penne pasta, ketchup, mustard, and steak seasoning to pan. Stir for an additional 2 minutes on low heat to fully combine.
Lightly coat a glass casserole dish with olive oil spray. Transfer mixture from pan to glass dish. Top with cheddar cheese, bacon, and green onion.
Bake for 10-12 minutes to allow cheese to melt. Optional: you may garnish with additional green onion and cheese once in serving bowls. Serve immediately. Enjoy!