The Welshman inherited the lead on SS2 when Toyota GR Yaris team-mate Rovanperä - winner of the first stage - exited in dramatic fashion.
Rovanperä understeered into a drainage ditch on the outside of a left-hand corner which pitched the car into a spectacular barrel roll. While he and co-driver Jonne Halttunen emerged unscathed, their hopes of sealing the title this week are over.
Evans, armed with a slight advantage obtained during the opener, was left duelling with Hyundai Motorsport’s Tänak. Neither felt 100 per cent comfortable on the fast and narrow Flanders farm lanes and there was little to split the pair.
Tänak was aided by a cleaner surface from first on the road and whittled his rival’s advantage down to just six-tenths of a second by the penultimate test. Evans then responded by shading the Estonian at Langemark to carry a 2.3sec buffer into the afternoon’s loop of four repeated stages.
"It was pretty okay to be honest,” Evans said of his Langemark charge. “We were finding a better balance between being clean and pushing.”
“I am happy with my driving, but of course this is only very early and there is still a long way to go," he added.
Local favourite Thierry Neuville completed the top three 6.5sec further back after a shaky start in his Hyundai. An overshoot in SS1 cost the Belgian around 10 seconds and, despite winning a stage, he lacked confidence.
"It's so different compared to last year and I am struggling so much to find the confidence,” Neuville explained. “I don't feel good in the car at the moment - I have a lot of diff openings and the wheels are locking under braking.”
Yaris man Esapekka Lappi trailed Neuville by 12.4sec in fourth overall. He was the last lucky driver to complete the final stage in dry conditions and seized the position from Adrien Fourmaux, who dropped over one minute while tiptoeing through the standing water.
Just 4.2sec behind in fifth overall was a frustrated Craig Breen, who also overshot in the first test. He promised big set-up changes at the mid-leg service and headed M-Sport Ford Puma team-mate Gus Greensmith by 32.8sec.
Oliver Solberg took on a conservative approach off the back of his Finland retirement to hold seventh in front of Fourmaux, while WRC2 frontrunners Andreas Mikkelsen and Yohan Rossel completed the leaderboard.
Takamoto Katsuta languishes more than four minutes off the pace after nursing a transmission issue on his Yaris. At times, the Japanese driver had to switch to EV mode to make it back to service.
• Full coverage from Ypres Rally Belgium is available on WRC+ All Live here, including every stage broadcast as it happens as well as key interviews, features and expert analysis from the service park.