Definitly Red left The Last Samuri trailing 14 lengths behind as the Grand National rivals went up against each other in Doncaster's Grimthorpe Chase.
Jockey Danny Cook guided Definitly Red away from the rest of the field while The Last Samuri - runner up in the 2016 Grand National - moved from fourth to second in the closing stages.
Wakanda finished in third place ahead of Sego Success.
"Hopefully now all roads lead to the National," said Cook.
"I think he's a very good horse and the question is whether he can jump round there."
BBC horse racing correspondent Cornelius Lysaght
The first two have thrown down significant markers for Aintree - although neither is going to earn anyone 10/10 for spelling.
If Definitly Red adapts to the very different obstacles on the Grand National course - and he has come to grief over 'standard' jumps twice in the last year - then judged by this, and with a nice weight (10 stone 11), he'll be a player.
The Last Samuri, second top-weight for the National on 8 April after last year's heroics, ran a funny sort of race, struggling before staying on. With likely drier conditions on a track he relishes, he is almost bound to go well again at Aintree.