sorry, I just realized I had this wrong...
Power comes from panel to (old) switch. From switch to another outlet below the sink (for disposal).
I removed the old switch and connected wires together so outlet below sink is always hot. (will be using air sink switch for disposal).
So now I have a double box above the countertop that currently has one GFI outlet (powered from a different circuit). Can I put another GFI next to it? And how should I power it up?
I hope this makes more sense...
If I cant add another GFI I can always just cover the open side of the box (we havent installed the backsplash yet) Not sure abuot the best way to cover it up though.