This past September, we celebrated my wife's birthday in Granada with dinner at a restaurant Rick ate at on one of his videos, Estrellas de San Nicolas. They have a web site where you can check the menu. This restaurant is high on a hill and overlooks the Alhambra. When the outer walls of the Alhambra are lit at night, you cannot beat the view. It is stunning. The food is of high quality. You can check to see if it is in your price range. They have an outdoor upper terrace with a clear view for everyone of the Alhambra. Inside, on a lower level, there are two large windows that also look out in that direction, but there are only two tables there. In warm weather those two windows are completely removed so you feel like you are outdoors. The other tables in that room do not have the best view.
I emailed them early, told them it was my wife's birthday and requested a table on the terrace or at one of the windows. They did not disappoint. Make sure you tell them it is a special occasion. I know two couples that are in Spain right now and they have both booked this restaurant on my recommendation. In my view, tapas for a 50th birthday just does not cut it. This is a special day. Spend a bit more and have something to really remember. Don't forget to take your camera!