Dawson hammered 14 fours and four sixes in his 107, while Ryan Baldry also hammered 57 as they hit a winning 207-4 from 20.2 overs, Tom Fletcher-Varey taking 3-40.
Brompton had posted 206-8, skipper Tom Pateman hitting 48, Fletcher-Varey 35 and Gabriel McGill 31, Baldry, Stu Neilson and Tom Watson bagging two wickets apiece.
Cayton earned a 37-run win at home to Seamer.
Skipper Michael Dennis led the way with 67 for Cayton, Jake McAleese (37), Ryan Woodhead (36) and Harry Holden (28) firing them to 227, Matty Walters taking 4-34.
Captain Gregg Chadwick hit 50, Rory Skelton 30 and Dave Graham 26 in reply but Seamer were all out for 190, McAleese scooping 3-22.
Scalby secured a 39-run home win against Staithes
Brett Cunningham’s undefeated 67 from 54 balls led Scalby to 246-7, with Ben Luntley and Brad Walker adding 53 each and Jon Barton 25.
Paul Theaker (3-57) was the top Staithes bowler.
Liam Cousins (4-40) and James Deaves (3-60) linked up to dismiss Staithes for 207, Ben Hoggarth hitting 54 and Simon Bowes 48.
Callum Battams’ 5-18 guided Bridlington 2nds to a four-wicket win at Staxton.
Battams helped skittle the hosts for 110, Kev Armstrong top-scoring with 48.
Rich Lount (42) and Tom McMeeken (33) helped Brid to victory despite Tom Pratt’s 3-31.
Mulgrave won by six wickets in their trip to Cloughton.
Cameron Anderson’s superb innings of 121 from 100 balls helped Folkton & Flixton 2nds to a 153-run win at Sewerby in Division One.
Flixton looked in deep trouble at 26-5 but a stunning stand of 173 for the sixth wicket between Anderson and Noman Shabir (58) helped them reach 245 all out.
Ted Traves took a cracking 5-22 for Sewerby.
Chris Mann and Lee Elvidge then took three wickets apiece as Sewerby were all out for 92 in 36 overs, Michael Artley top-scoring with 30.
Heslerton secured a 126-run win at home to Thornton Dale.
Skipper Tom Benthall led by example with 81no, with Ryan Wharton adding 64 and Kristian Wilkinson 58 in their 250-2.
Marc Dring (3-7), Harry Edwards (3-39) and Matty Webster (3-20) helped dismiss Dale for 124, Tom Snowdon top-scoring with 25.
Settrington had to dig deep for a two-wicket home win against Forge Valley.
Skipper Sean Pinder top-scored with 57 for Valley, John Flinton also making 29, but they slipped from 103-1 to 155 all out, Jack Corner and Eddy Rounthwaite snapping up three wickets apiece.
Alex Glass kept Valley in the game with 5-25, but 48 not out from captain Stephen Beal made sure of the win with two wickets and 8.4 overs to spare, Richard Reynolds having earlier hit 36.
Doug Bentley’s 89, along with four wickets apiece from Sam Burns and Ryan Boyes earned Great Habton a 124-run success at Sherburn.
Habton posted 207-5 thanks in main to Bentley and the hosts were then skittled for 83.
Wykeham racked up a nine-wicket win at home to Cayton 2nds.
Adam Eustace and Tom Owen took three wickets each as Wykeham dismissed Cayton for 130, Toby Jones hitting 38.
An opening stand of 93 between Ezra Pashby (49) and Mike Dugdale (55no) secured the win for the hosts.