To pulverize nuts in a food processor without turning them to paste, be sure that the processor bowl and blade are dry and cool (not hot from the dishwasher) and the nuts are at room temperature (not cold from the fridge or freezer and not hot from toasting in the oven). Pulse until the nuts are as finely ground as you like, scraping the sides and corners of the processor bowl with a chopstick from time to time.
If you follow these rules, there is no need to add flour or sugar from the recipe to keep the nuts from turning to butter, as is sometimes advised, although there is no harm in doing that either!
p.s. You can also make a fluffy nut flour or nut meal in the processor, using the fine shredding disk instead of the steel blade: the same precautions about the temperature of the nuts and the disk apply.