Put yogurt, lemon juice, rice wine vinegar, ketchup, soy sauce, onion, garlic, ginger paste, sugar, and black pepper in a blender; blend on High until smooth.
Pour dressing into a sealable container, seal, and refrigerate at least 30 minute before serving.
Cook's Notes:
I use low sodium soy sauce, so if you're using regular soy sauce, you may want to cut back a bit.
You also may desire to cut back on the amount of garlic and onions or saute them first to give a milder taste.
If you are using fresh ginger, you may want to reduce that amount.
If you are using Greek yogurt, you may want to add some water.