Fat free greek yogurt with chia seeds. Million things you can build on it. Mainly I use sugarfree protein isolate and/or peanut butter powder, some oats and spices. I only eat lunch + dinner so it's a healthy dessert.

Get a pressure cooker, make stews fast and pack them into serving sizes for lunches at work/school or leave it in a large contain and serve it for dinners for days.

I prep my vegetables like carrots, celery and mushrooms and then freeze them. When I want to make a stew I take the pressure cooker pot to the freezer and fill it with the veg I want and get protein I want then add stock and seal the cooker and set it for 28 mins on high pressure and I get a stew that would take a few hours on the stovetop.

I like to do Ethan Cheblowski's Sunday braise (description starts at around 7:45). I braise meat with some veggies, blend the vegetables into a sauce and use spice mixtures throughout the week. Sometimes I eat the meat and the sauce with some roast potatoes, sometimes I reheat the meat in tomato sauce with Italian seasoning and have it with pasta.