The playmaker helped himself to two assists for Cyriel Dessers as Philippe Clement’s side saw off Hearts 2-0 at the national stadium.
It means the Gers will face Old Firm rivals Celtic in the Scottish Cup final on May 25.
But Cantwell says the squad won’t even think about that game as they will put their full attention on Premiership duty.
Speaking to RangersTV, he said: “The plan was to go to Hampden and win and we have done that. We are excited to get to another final.
“We have finals every game now and we have to win every one of them. If we do then we will be in a good place at the end of it.
“We started well, the early goal helped. No team will turn down an early goal as it puts you in a good position and it steadied us a little bit.
“We had a tough week so to start well was great and in the first half, we were pretty dominant.
“Hearts are a good side and they had a little spell in the second half but we showed our quality in certain moments.
“I wasn’t expecting to have that much space at times. The way we set up, we try to get me on the ball, sometimes it is harder than others.
“Teams tend to drop off against us and it can be difficult, Hearts came to press us.
“But we are comfortable playing out with the ball and that showed.”
Nigerian international Dessers fired the team ahead inside five minutes at Hampden, before sealing their final spot with another calm finish in the closing stages.
Cantwell admits he had planned to go for goal himself after a superb driving run from midfield but decided to help his team-mate notch his 19th strike of the season.
He added: “I was pleased with my performance. I have said it time and again, I am in the team to make things happen.
“It is my responsibility to find a way to break down teams and we did.
“Did I think about taking it on myself for Cyriel’s second goal? Yes, it was in my head the whole time to be honest.
“I heard and saw Cyriel running out of the corner of my eye and if I am being honest, at that point, I hadn’t looked at the goal. So I thought ‘please score this Cyriel’.
“In situations like that, I am quite unselfish and I look for the pass, but in a smart way.
“Everyone thought I would shoot but I played it to him to score.
“I’m really pleased for him to get two goals. Cyriel will always work hard and do what he is in the team to do.
“His numbers speak for themselves, there is a lot of talk about him and how he plays.
“Sunday is the evidence that he is great for us, he works hard and he is a fantastic lad who scores goals.”