Into a bowl, add the condensed milk, the whole milk, and the lime juice, mix well until combined.
Dissolve the unflavored gelatin powder in the microwave for 30 seconds and add it to the bowl, once dissolved. Mix for 1 minute.
Evenly grease a ring cake mold with one drizzle of oil (it doesn't give the dessert an oily taste), pour the mixture into the mold and let it chill in the fridge for at least 4 hours.
Run a knife along the edges and the center to help unmold.
Top it with lime zest to taste.
Serve.