Trim greens from ramps; reserve for another use. Place buttermilk in a shallow dish. Combine flour, salt, black pepper, and cayenne in another shallow dish. Coat ramps in flour mixture, then buttermilk, then flour mixture again.
Fit a large pot with a deep-fry thermometer. Pour in oil to a depth of 2″; heat over medium-high until thermometer registers 350°. Fry ramps until golden and crisp, about 2 minutes. Drain on paper towels; season with salt. Serve with lemon wedges.