I forget to eat and I do think it's related to ADHD though obviously I recognise not every single person with ADHD has the same issue! For me it's a combination of time blindness and I just don't get very hungry. I couldn't be doing with eating 5-6 meals though, I would eat half a cow once a week if I could. It's all the faff around food that I don't like.
Air fryers are great for quickly doing things like sausages or chicken nuggets/goujons to go with things.
Bacon, mushroom and fried egg sandwich is my go to.
Instant noodles like the ramen packets can be jazzed up with some tinned sweetcorn, frozen peas, ripped up ham, small-chopped vegetables like spring onion, peppers, mushrooms etc - put them all under the noodles when you put the hot water into the bowl. DS1 also cooks his in a saucepan and stirs a raw egg in as it's cooking so it sort of scrambles or poaches into the noodles, which is a nice way to make them more filling. Or add the air fryer nuggets and some sweet chilli sauce.
Very millennial of me but half an avocado squished onto a bit of toast or nice fancy bread, with some bacon or egg on top if I feel like adding more.
Museli in a bowl with yoghurt stirred through and topped with fresh fruit. Add some milk if it's still too dry.
Porridge with frozen berries, made in microwave. Equal amounts oats and milk, throw some berries in, microwave for ~2 mins (if there are big chunky strawberries, microwave separately first), stir, back in microwave for a min or two, add more cold milk to cool it down, stir in some honey or sugar. My sister says porridge is magic because if it's too thin then you can either microwave it more or just leave it to stand and if it's too thick you can add more milk.
Stir fries are easy and quick. With microwave rice, or a rice cooker is amazing or instant noodles. "Minute" steaks cook through really quickly. Kitchen scissors are a way to cut meat without handling it too much.
Tuna pasta salad. Pesto pasta with or without air fried sausage or veg. Marmite pasta. Buttered pasta with a bit of salt and pepper! Actually there are loads of simple pasta dishes which barely take any time to make. I used to have a huge pinterest board with so many of them. Ready made pasta sauces can also be time saving.
Microwave jacket potato, finish off in oven or air fryer ~20 mins. Fill with beans or tuna or leftovers or whatever you like.