What do you mean by summer sauce?

Once upon a time, there was a yellow sauce and Chili sauce living together, but the relationship was not good. They had to fight every day as soon as they met, but every time they were beaten with yellow sauce, they all lost. So they made a wish to God, hoping to become stronger, and God granted their wish. Guess what? ""Yellow sauce turned into summer sauce. "

It's hard to see what it means if you look closely.