Chop bacon and add to a cast iron skillet or Dutch oven on medium heat and begin to cook.
While the bacon begins to cook, dice an onion and add it to the cooking bacon.
Open the cans of green beans, drain thoroughly, then add them to a large bowl.
Once done, drain any renderings and add the cooked bacon and softened onions to the bowl of beans.
Stir the cream of mushroom soup until everything is well combined.
Stir in the cheddar cheese, lemon juice, and a quarter of the can of crispy fried onions. Take a taste and add any salt and pepper as needed.
Add the green bean mixture to the Dutch oven or skillet and smooth out, making it as even as possible.
Sprinkle the remaining crispy fried onions over the top.
Cover with foil or a lid and bake for 30 minutes, or until heated through.
Once heated through remove the covering and bake for an additional 5 minutes, allowing the fried onions to become golden brown.
Notes
Drain the beans hard. Empty the cans into a colander and let them sit in the sink, then shake before adding. Less water means a thicker, creamier casserole.
Hold back onions for the top. Stir only a quarter of the can into the mix and save the rest for the topping so they stay crisp.
Cover, then uncover. Bake covered for 30 minutes to heat through, then uncover for the last 5 so the onions turn golden.
Coming from the fridge? If you made it ahead, let it sit on the counter 30 to 60 minutes before baking, or the bake time can nearly triple.