I made a fruitcake consisting of primarily raisins and currants, grape juice, a little flour and egg to hold them together and spices. What bracha do I say to eat such a cake? The majority substance is clearly grapes and grape juice.

B"H
We have always learned that in such cases you make the blessing over the principal aggregate of that morsel which, in your case, are the grapes, and you fulfill thereby your duty of blessing over the adjunct - such as the pastry itself. Your intention is clearly in eating the fruit, and not so much the dough.

Sincerely,
David Ben-Abraham