Dacha Tactics #55 - Oozing dark.

This is from a game of mine in a blitz time scramble. We are up a whole bunch of material but the a7 pawn is about to queen. The normal response would be Ra2 and trade the rook for the pawn. Is there better? Let color money guide us! We have a beautiful golden Bishop with nice light bricks to boot. Any juicy clutch dark ideas?

Interact with the puzzle below.  If you get stuck, you can always click the "lightbulb" icon in the lower-left of the puzzle frame.  Good luck!

See IM Yaacov discuss the solution below.