Kyle Larson led the race when it was eventually called off due to the weather, and the 29-year-old will resume from the front on Monday, 17:00 BST.
After a poor start saw Denny Hamlin lose the lead to Chris Buescher around the first turn, the 41-year-old veteran regained the position after Buescher momentarily lost control of his car.
A competition caution on lap 40 allowed the field to check tyre wear, and once the green flag was waved on lap 46, Hamlin had built a two second lead on second-placed Larson, while last week's winner at Talladega - Ross Chastain - was running in third.
Larson eventually did stick the move for the lead, and the California-born driver wasn't forced to lead for long as rain rolled in and the session was red-flagged.
Having completed just 78 of the 400 laps at Dover, the race will resume on Monday, where Larson will look to hold onto his lead.
Currently in the standings, Chevy driver Chase Elliott sits atop the NASCAR Cup Series with 2,017 points, with Ryan Blaney right behind him at 2,013 points. Elliott's No. 9 car started from the fourth position, whereas Blaney was right behind him at No. 5.
Upon resumption, Larson leads, with Elliott, Blaney, Martin Truex Jr., and William Byron comprising the top five.