With a paring knife, cut a shallow x in the bottom of the tomatoes. Bring a medium saucepan of water to a boil. Add tomatoes and boil 30 seconds. Using a slotted spoon, transfer tomatoes to a bowl. When cool enough to handle, peel and discard their skin. Cut tomatoes into quarters lengthwise. Using your fingers, discard seeds. Transfer tomatoes to a blender.
Add vinegar, sugar, garlic, and paprika and puree until smooth. Remove the center cap, and with the motor running, add oil in a steady stream, blending well. Season with salt and pepper.