Begin by slicing the fresh passionfruit in half, using a spoon to scoop out the vibrant pulp and seeds into a mixing bowl. Combine the pulp with sugar and freshly squeezed lemon juice, stirring gently until the sugar dissolves. Set this tropical mixture aside for now.

In a medium saucepan over medium heat, pour in the whole milk and half of the heavy cream. Stir occasionally as the mixture heats until it starts to steam but doesn't boil, about 5-7 minutes. Remove it from heat and set aside as it cools slightly.

In a separate bowl, vigorously whisk together the egg yolks and the remaining sugar until the mixture is pale and slightly thickened, about 2-3 minutes. Gradually temper the heated milk mixture by whisking in a spoonful at a time. Once combined, return the entire mixture to the saucepan over low heat, stirring gently until it thickens and coats the back of a spoon, reaching about 170°F.

Once the custard is ready, pour it through a fine mesh strainer into a clean bowl to remove any lumps. Stir in the remaining heavy cream, vanilla extract, and a pinch of salt, mixing until well combined. Finally, gently fold in the passionfruit mixture.

Cover the bowl with plastic wrap and place it in the refrigerator to chill thoroughly for at least 4 hours, but overnight is even better.

Once chilled, transfer the custard into an ice cream maker. Churn according to the manufacturer's instructions until the ice cream reaches a soft-serve consistency, typically around 20-25 minutes.

After churning, transfer the passionfruit ice cream into an airtight container. Spread it out evenly and freeze for at least 2 hours to firm up.