Preheat oven to 280°F (140°C).

Make the caramel: Add sugar, water, and lemon juice to a pot and cook over medium heat without stirring until it turns an amber color. Carefully divide caramel into 6 containers (about 1 cup / 250 ml each) and swirl to coat about halfway up the sides. Set aside.

Make the custard: In a bowl, gently whisk eggs, condensed milk, and vanilla just until combined (avoid incorporating air). Pour in the milk and gently mix again. Strain the mixture to remove lumps, then pour into the caramel-lined containers, leaving a little less than 1/2 inch (1.3 cm) headspace.

Bake: Cover each container with aluminum foil. Place in a deep baking tray and add hot water to the tray until it comes about halfway up the sides (bain-marie). Bake for 60 minutes, or until set but still wiggly. Remove from the water bath, cool to room temperature, then refrigerate overnight (minimum 8 hours).

To serve: Loosen the edges, warm the bottoms briefly (or dip in warm water) to melt the caramel, then invert onto plates.