Fry the tostones according to the package directions.
Mash the avacados, add a diced tomato, a diced red onion, salt to taste, and a splash of lime juice.
Cube the tuna and marinate it in teriyaki sauce for a few minutes. Then roll each piece of tuna in black and white sesame seeds.
Grill the tuna on a greased grill pan for a few minutes on each side. The outside should be well done while the inside remains rare.
Spread the gaucamole on each tostone and top with a piece of tuna.
Mix the sour cream, heavy cream, and juice from half a lime in a bowl. Transfer the crema into a squeeze bottle, and squeeze it on top of your tuna tostones. Garnish with fresh cilantro.