The 20-year-old broke the deadlock at Children's Mercy Park on 25 minutes, heading home a Graham Zusi cross.
The goal was the winger's third in the cup competition, having also netted three goals in Major League Soccer thus far this campaign.
The former Liberty Professionals man, who joined the US-based club in February this year, however, saw his night cut short by a thigh injury two minutes to half-time.
Having replaced the Ghanaian, Daniel Salloi made it 2-0 for KC on 66 minutes before Bradley Wright-Phillips pulled a goal back for Red Bulls in injury time.
The victory makes it four Open Cup titles for KC in history and their third since 2012.
"To get the goal, great goal, beautiful cross, excellent run by Latif [Blessing]," coach Peter Vermes said.
"I feel bad for him and Gerso coming off because of injuries, even [Diego] Rubio.
"But, look, all those guys punched the clock tonight. Everybody put everything in they had."
Red Bulls coach Jesse Marsch, however, rued Blessing's effort.
“We put Kemar Lawrence out there to make sure that [Graham] Zusi wouldn’t have freedom to be moving into the attack and putting balls into the box," the manager said.
"We were late to rotate out there and somehow it winds up just going over Aaron Long’s head and right to Blessing. So it was a good finish, but it shouldn’t have gotten to that. We should have done better."
Red Bulls goalkeeper Ryan Meara shared his coach's sentiments.
“[Graham] Zusi put a real good ball in and it just kind of got over Aaron (Long) and he [Blessing] just had a powerful header on goal," the shot-stopper opined.
"That’s a play that you just have to credit them, they made a nice play, as simple as that.”