In a stock pot bring the V8 juice and 1 cup water to a boil, then reduce heat to low and keep warm. While stock is warming, cook chorizo through in a saute pan - set aside juices and all.
In a large saucepan, melt 2 tablesponns butter and saute the onions over medium heat until translucent. Season with salt and pepper and the cayenne pepper.
Add the arborio rice to the onions and cook, stirring constantly for 2 minutes. Then add the wine and cook for about 1 minute or until the wine is absorbed, stirring constantly.
Pour in 1/2 of the V8 mixture, stirring occasionally until most of the liquid is absorbed (about 10 minutes). Mix in the chorizo and juices as well as the remaining V8 mixture and cook for another 10 minutes or until the liquid is mostly absorbed.
Remove risotto from heat and add the remaining 2 tablespoons of butter as well as the parmesan cheese, stirring until melted.