The Rapids moved into first place in the Western Conference.
Cummings took a low crossing pass from Colin Clark and scored in the 65th minute for his third goal of the season. Gomez came through on a penalty kick with eight minutes left in the game.
All but one of Colorado's 13 goals this season have been scored in the second half.
Colorado improved to 4-4-0 while Salt Lake fell to 2-4-2.