Ceviche Tostadas with Cilantro Cream

Name: Ceviche Tostadas with Cilantro Cream
Ingredients: * 1 pound skinless white fish (halibut, tilapia, whitefish, snapper,; bass are good option),; * 1 small white onion, chopped into piece; * 1 1/2 cup freshly squeezed lime juice (from about 12 lime); * 1 large jalapeno, stemmed, seeded and finely chopped; * 1 rip, fat tomato, cored, seeded and; * 1/4 cup loosely packed cilantro leaf, chopped; * 2 tablespoon extra virgin olive oil; * 1 teaspoon sugar; * kosher salt; * for the cilantro cream:; * 3 cup loosely packed cilantro leaf; * 1 tablespoon freshly squeezed lime juice; * 1/2 cup mayonnaise