To prepare the sauce for the Burger. The Cubans are very fond of this sauce and I believe that it is a perfect combination of bun, meat and potatoes.
For the sauce, dilute the tomato paste with water, add crushed cumin, paprika, garlic powder, wine vinegar, sugar and salt. Cook to your taste, try and put what is missing. The sauce should be sweet and sour and spicy. And delicious.