If I double this recipe as suggested what is the correct baking time for the larger size? Thanks.

If you use a larger cake pan and it's still the same height, it's a similar time. That said, a well known version of Elizabeth David's chocolate and almond cake (which is very similar to this Torta caprese) by Jill Dupleix is about double the amount of recipes and calls for 40-50 minutes baking in a 20cm tin at a slightly higher temperature (180C/350F). I would go follow that but keep an eye on it and check with a skewer for doneness - you want crumbs that still cling to the skewer so that it is quite moist inside.