Cardiff City scored three second-half goals to secure a place in the semi-finals of the FAW Premier Cup.
City fielded a shadow side, giving the majority of their squad a run-out.
Des Hamilton played his first game for over a month, while Leon Jeanne was included up front.
Jeanne was involved in the first attack, which saw youngster Tony Wallis' header blocked.
Newtown fought back, though, to dominate the half and City keeper Lee Kendall had to make impressive saves from Scott Williams and Chris Adamson.
Fine run
City were forced to replace injured Martyn Giles with Kirk Huggins, and the under-19s player was soon in the action hooking away an Adamson shot.
Two players were booked in a disappointing first half - Newtown's Justin Bridges (foul) and Cardiff's James Collins (diving).
Cardiff upped a gear after the break and took the lead in the 53rd minute when a fine run and cross by Kevin Evans saw Jeanne head in at the far post.
Newtown had a great chance to equalise ten minutes later when Steve McCormick was tackled by David Hughes, and City went straight up the other end to score.
A long ball by Wallis saw Collins control on his chest and fire home from 20 yards.
And things got worse for Newtown when McCormick blazed a penalty over the bar after Hamilton had fouled Justin Wickham.
Cardiff rounded things off with a fine 87th minute goal from Wallis, after some sparkling footwork by Hamilton.
