Place onions in a bowl. Combine red wine vinegar, ½ cup water, and sugar in a saucepan. Place over high heat and cook, stirring until mixture boils. Pour brine over onions and set aside for 30 minutes.

In a small bowl, whisk together sour cream, lime zest and juice, and a pinch of salt.

Pour an inch of canola oil into a heavy-bottomed skillet placed over medium heat. When oil reaches 375°, slide plantains into it. Fry until lightly golden, 5 minutes per side. Transfer plantains to a flattened paper bag, then use the bottom of a mug to flatten each slice. Return slices to hot oil and fry until golden brown, 2 minutes. Transfer plantains back to flattened paper bag. Generously salt them while hot.

To assemble each stack, place a sausage round on top of a fried plantain slice. Top with cream, pickled onion, and cilantro leaf. Repeat as necessary. Serve immediately.