Whisk all ingredients together in a bowl, and add fresh rosemary-optional.
Then cover with a kitchen towel. Let sit for 30 mins to 2 hours to soften the socca. I have left it all day, and it is just as good.
Preheat oven to 450 degrees. Generously coat a cast iron or regular pan but not non-stick. A cast-iron pan is ideal, you can also use a crêpe pan.
Coat the pan generously with olive oil and warm in the oven for 10 minutes. Remove the pan from the oven (using an oven mitt, of course)
Wisk the socca again. This is necessary after it has been sitting for any length of time.
Pour batter into the hot pan. Put the pan back in the oven and bake. It takes about 15-20 minutes to bake, depending on the size of the pan and your oven. It is done when the edges start to crisp.
Top with sea salt and serve. See notes for other serving ideas.
If you are using a crepe pan, you can split the batter and make two.