• Preheat the oven to 140℃.
• Use a food processor to blitz the digestive biscuits to a fine crumb. Alternatively, place them into a sandwich bag and smash with a rolling pin.
• Melt the butter, pour it over the crushed biscuits and mix well until it resembles wet sand.
• Press it down into an 18 cm springform tin. Press it into the edges so that it has a 1-2cm high edge.
• Place it into the fridge whilst you get the filling ready.
• Separate the egg yolks from the whites, set the egg whites aside, you will use it for the meringue later.
• Add the egg yolks into a mixing bowl, pour in the condensed milk, then add the zest and juice of the lemons.
• Beat it with a whisk for a few minutes until completely smooth.
• Bake it for 15 minutes.
• Leave it to cool to room temperature before placing it into the fridge to set for at least 2 hours.

Meringue:

• Add the egg whites into a large mixing bowl along with the cream of tartar. Beat it with an electric whisk until it reaches soft peaks.
• Meanwhile, add the sugar and water into a saucepan and boil rapidly over a high heat. Use a thermometer to read the temperature, it needs to reach 115℃.
• Slowly pour the sugar syrup into the egg whites whilst still whisking the meringue. Once you have poured all the sugar syrup in, beat on the highest setting until it has stiffened up.
• Spoon as much as you would like over the top of the pie. Then use a chefs blowtorch to create the golden colour on top. If you don't have a blowtorch you can pop it under a hot grill instead.