ALTOONA, Iowa -- Cornfed, ridden confidently by the meet's leading rider, Ramon Vazquez, surged clear into the stretch and cruised to a 4 1/4-length win in Sunday's $69,975 Iowa Stallion Futurity at Prairie Meadows.   Cornfed, an easy victor of his lone previous start in a May 9 maiden locally, raced in striking position while four wide on the turn in the 12-horse field. Given his cue by Vazquez, who was winning for the eighth time this weekend, Cornfed swept to the front and was not fully extended to hold the Lone Star Park-based filly Another Bond Girl safe. Billie Boy stayed on well to grab third, three-quarters of a length behind Another Bond Girl.  The favored Cornfed ($4.60), a 2-year-old Pass Rush gelding who was one of six Iowa-breds in the field, covered 5 ½ furlongs in 1:05.89. Trained by Ray Ashford Jr., Cornfed will be pointed to the $75,000 Iowa Cradle Stakes on Aug. 8.  Bred and owned by Jeff Hartz's Runaway Racing LLC, Cornfed collected $42,750 for the win.