To make things even easier, you sure can! However, if you have the 5 minutes to make a homemade batch, I do recommend it! As a recent commenter said, "I finally decided to make romesco instead of buying it and I can't believe I waited so long and definitely won't be going back to the premade version. So easy and so good!" TDLR; you can in a pinch, but go homemade if you can.