Bring medium pot salted water to boil. Add pearl onions, blanch 2 minutes. Drain slotted spoon into ice bath bowl. Peel skins easy pinch fingers once cool.
Heat olive oil in skillet medium using measuring spoon. Add minced garlic and red pepper flakes, cook 1 minute fragrant wooden spoon.
Pour vodka careful, tilt pan slight flame if gas or light match safe distance. Simmer 2 minutes alcohol burns off, stir wooden spoon.
Stir crushed tomatoes, salt, pepper from measuring spoons. Simmer 5 minutes thick. Add peeled pearl onions, coat even. Pour heavy cream, simmer 10 minutes till sauce clings glossy.
Stir parmesan till melted smooth. Taste adjust salt. Pull heat