Heat the butter in a large non-stick frying pan on high until the butter melted and is just starting to turn golden.
Add the shrimp and cook until they are almost opaque all the way through; stirring frequently after the first two minutes. Shrimp overcook very easily, so be sure not to cook them too long.
Add the garlic, light green onions first. Cook for a few more minutes on medium heat, then finish with the tomatoes and dark green onions for a few more minutes.
Remove from heat and squeeze in the lemon juice and season with salt & pepper to taste.