Newcastle's youngsters trailed in the early stages of their Group C encounter at the LNER Community, following Joe Felix's strike, but went into the break on level terms courtesy of Vakhtang Salia's finish after Dowell produced a handful of impressive first-half stops.
Second-half strikes from Kyran Thompson and Afner Cá secured the club's first EFL Trophy inside 90 minutes since November 2018, with the attacking duo netting their first goals for Newcastle's Under-21s in the process.
Dowell, one of eight teenagers to sign a full-time scholarship with the Magpies last summer, said: "We had to weather the storm a bit as we were always expecting them to put it on us in the first half.
"We knew we weren't going to have the ball as much but I think the lads were top. On the counter-attack, that's what we knew we were going to have and it's unbelievable to get the win.
"When we went one-nil down, it was more about keeping our heads. It's easy to go under from there, especially early doors, so everyone did well to stay in the game and we started playing.
"We got a lucky goal before half-time and that did us the world of good. We needed that so much and the lads, at half-time, were saying how much it lifted us. It was massive and starting quickly in the second half was vital."
Dowell, who joined Newcastle's Academy at Under-9 level, has relished the step from Under-18s to Under-21s football and made his full debut at second-string level during last week's National League Cup clash against defending champions Boreham Wood.
The Boldon-born shot-stopper, who made his England Under-17s debut as a 15-year-old, believes the experiences gained against senior opposition can only benefit him in the fledgling stages of his career.
"When I've come from the Under-18s to Under-21s, I try not to do anything different," he explained. "I was playing well for the Under-18s so I wasn't going to look for work and just do the same as the Under-18s for the Under-21s.
"The last two games I've played have probably been my most enjoyable in so long. I always enjoy it but there's a bit more on it; it's a men's team with a lot of fans and I quite like that. I'm really happy with where I am and hopefully I can kick on.
"These experiences are massive for me. You grow every game and realise what the top professionals do. It's different to Academy football and physicality is the biggest thing but I think it's key for my development."
Dowell, who cites Manuel Neuer as his footballing idol, revealed the healthy competition for the number one role alongside fellow 16-year-old George Mair has elevated both of their games further within the Magpies' youth set-up.
He explained: "The training sessions are always competitive! I'm mates with George, we get on, but in training it's about who is beating who?
"I don't think we'd be as good without each other because we push each everyday in ridiculous amounts. That's massive in both of our developments."

