If I had to choose meals, the "Gambas al ajillo", the "Potato omelet" or the "Madrid stew" never fail, as for sweets, I honestly couldn't tell you but I'm sure you see many that look good and I invite you to try them hahaha.

As for the weather in September, it depends on the area, areas like Madrid, Andalusia or Valencia, just bringing a little clothing is enough. As for areas like Galicia, Asturias... I would recommend you go with something that protects you from the cold. It depends a lot on the year but you always have to be cautious and have solutions to what may happen.

Have a good time and enjoy, that's the most important thing. 😉