Okay, after doing some testing, it seems that there are indeed foods which are super easy to grow.
This is the list of best 5:
1. Peas
Pea plant grows almost anywhere you plant it. All you have to do is plant it in early spring or late winter.
I have even planted some with no tilling at all. I just put a hand of soil on ground between grass, place two or three seeds and cover lightly.
2. Raspberries
Raspberries grow on their own once you plant them. Once they grow into a bush, its lots of free food every spring or summer.
3. Hazel
Probably the best tree to grow. It takes very little space, produces hazelnuts which are high in calories and can last long without spoiling.
4.Walnut
Some people dont like walnut trees because they grow so big. I guess thats their only flaw. Other than that, once planted, they just grow on their own.
5. Apple
I would say for sure that apple is easy to grow. There are even dwarf varieties which produce fruit just year after planting, so you dont even have to wait.