The present disclosure is directed to a rotor blade for a gas turbine engine. The rotor blade includes a platform comprising a radially inner surface, an undulating radially outer surface, a leading edge portion, a trailing edge portion, a pressure-side slash face, and a suction-side slash face. An airfoil extends outwardly from the undulating radially outer surface of the platform to an airfoil tip. A connection portion extends radially inwardly from the radially inner surface of the platform. The platform, the airfoil, and the connection portion collectively define a cooling circuit extending from an inlet in the connection portion through the airfoil to a plurality of outlet plena in the platform. Two or more outlet plena of the plurality of outlet plena are spaced equidistant from the undulating radially outer surface of the platform.