Green onions are ridiculously easy to grow and I use them a lot in my cooking.
I cut off the green part of some store bought green onions (to cook with) and rubber banded the white bottoms together. Then, I cut the top off a water bottle, filled it half way with water, and threw the white bundle into the water. It’s sitting on my window sill, but my apt is on the ground level, so I actually keep my shutters closed 95% of the time. They barely need any sunlight to flourish. Look at the progress after only a week!