Whats a Spanish dish that is easy to make and can feed a lot of people?

My Spanish cl is having a fiesta and whoever brings some authentic Spanish food gets extra credit (y necesito esta muy mucho). So I'd really appreciate if you'd let me know any Spanish dishes that I could make easily and are not too expensive. And there will be about 40 people but there will be a lot of other foods from other cultures so there doesn't need enough for everyone. But I'd like it to feed at least 20 people. Please help and thanks!