Make the sour cream dip by combining all the ingredients in a small bowl. Set aside.
Using a box grater, coarsely grate the potatoes and onion and place them in a clean tea towel. Squeeze out as much of the liquid as possible.
Lightly beat the eggs in a large bowl, then whisk in flour. Add the grated potatoes, onions and Ribeye Roast Rub, and season with salt and freshly ground black pepper to taste. Using a wooden spoon or hands, mix well to combine, but do not overwork.
Heat the oil and butter in a large, non-stick pan over medium heat, until it’s hot but not smoking. Place four scant ¼ cup portions of potato mixture into the pan and flatten them with a spatula until they are about 1cm thick.
Fry until the cake bottoms are golden-brown, about 4–5 minutes. Flip them over and fry until the other side is also golden-brown and crisp, an additional 4–5 minutes. Repeat with the remaining mixture. Transfer to a plate lined with paper towel to drain the excess oil. Serve immediately with the sour cream dip.
