Bradford were the first team to beat Cardiff this season, winning 3-1 in the Welsh capital in September.
By avenging that defeat in Yorkshire on Saturday, Turnbull believes his team underlined their promotion credentials.
“It’s a huge win,” he said. “We knew coming here, they turned us over at our place, so we wanted to show them we’re a better team than we showed that day.
“We had to fight for it in the end. We played some great football in the first half, cut them open at times. It’s a massive result.”
Turnbull is a technically gifted player capable of scoring spectacular goals, but his long-range effort against Bradford was his first league goal since November 2024.
He also scored with a superb diving header against Chelsea in the EFL Cup in December, and the Scotland international hopes to add to his tally.
“I was going to strike it with my left, saw the defenders coming so chopped it and the rest is history,” Turnbull said of his goal at Valley Parade.
“I feel like I’m performing better each week. It’s about consistency now and doing it regularly. I feel like it is the best I’ve played, and as a team, since I’ve been here.”