Well, it's up to you. I stick to Paleo foods and avoid anything pro inflammatory, which narrows things a bit. You can eat junk, processed food and stay in keto, if that's your only goal. For me a typical day is:
Breakfast - smoked salmon with olives, cucumber, radish, added olive oil
Dinner - beef/fish/liver fried in coconut oil, spinach, kale, broccoli, olive oil
I don't eat lunch. You don't get hungry every few hours when you're in keto, so there's no need to eat every few hours.
There are other good sources of fat, like tree nuts (not peanuts) and eggs, but they can cause inflammation, and avocado which can cause indigestion (FODMAP). Cheese is mostly fat, if you tolerate dairy well, but most people don't.
There are many options, it really depends on your goals. If it's just keto, you can replace things like bread, pasta, rice, and potatoes on your plate with cheese and you're done
