For the cake:
Line an 8in (20cm) square pan with parchment paper. Set it aside.
Preheat the oven to 350°F (180°C) for about 5 minutes before baking the cake.
Place the eggs in a large bowl and mix for about 1 minute using a wire whisk.
Add the milk, vegetable oil, lime juice, lime zest, and lime gelatin powder. Whisk until well combined.
Sift the flour, sugar, baking powder, and salt over the mixture. Gently whisk until just combined and smooth. Don’t overmix the flour.
Pour the batter into the prepared pan and bake for about 30 minutes or until a toothpick inserted in the center comes out clean.
Allow the cake to cool completely at room temperature.

For the Lime Frosting:
Combine the condensed milk and lime juice in a medium bowl. Whisk until well combined.
Pour the hot water over the lime gelatin and stir until completely dissolved. Pour the melted gelatin into the condensed milk mixture and stir until well combined.
Spread the mixture over the cake and refrigerate for at least 2 hours.