Add the raspberries, sugar and lemon juice to a saucepan and bring to a boil while mashing the raspberries to break them down.
Once it boils, turn off the heat and adjust with more sugar or lemon juice to taste.
Strain the raspberry sauce through a fine mesh sleeve to remove the seeds. Press firmly to extract all the pulp as that is what thickens the sauce.
Chill the sauce in the fridge in a squirt bottle. The sauce will thicken as it cools.
Leftovers can remain in the refrigerator for up to 2 weeks in an airtight container. Leftovers can also be stored in the freezer, and reheated for future use.
Before serving this cheesecake, drizzle the raspberry sauce and top with fresh raspberries before serving.