Chop thawed strawberries into small pieces and strain excess liquid.

Place strawberries, sugar and the lemon juice in a medium saucepan and stir to mix.

Heat mixture over medium-low heat until the mixture starts to lightly simmer. Whisk constantly so the mixture doesn’t burn.

In a small bowl, stir the cornstarch and water together until the cornstarch is fully dissolved.

Whisk the cornstarch mixture into the saucepan of strawberry mixture. Whisk well to mix then bring mixture back to a light simmer. Let simmer for 1 minute so the mixture thickens a bit.

Remove the saucepan from the heat. Allow mixture to cool to room temperature before moving to next step.

Place room temperature strawberry cake filling into a medium bowl and cover with food-safe plastic wrap. Press the food-safe plastic wrap down against the top of the cake filling to prevent the cake filling from forming a thick film on top.

Place the strawberry cake filling into the fridge for at least 12 hours or overnight. This gives the filling a chance to thicken more before placing between cake layers.

Use the strawberry cake filling in a 3-layer cake (3 layers of cake with two layers of filling).

When placing strawberry cake filling on top of one of the cake layers, start with a ring of frosting around the outer edge of the cake layer. This well help the strawberry cake filling stay in the middle of the cake instead of coming out the sides when the cake layers are placed on top of each other.

Decorate cake as desired.

Refrigerate cake for at least an hour before serving.