In a large bowl, combine the flour, sugar, baking powder, salt, and cinnamon.
In a separate bowl, whisk together the eggs, milk, melted butter, and vanilla extract.
Pour the wet ingredients into the dry ingredients and stir until combined. The dough will be thick.
Heat vegetable oil in a deep fryer or large pot to 350°F (175°C).
Use a spoon to drop dollops of dough into the hot oil (don’t overcrowd). Fry for about 3-4 minutes per side or until golden brown. Remove from the oil and drain on paper towels.
Prepare the Strawberry Cheesecake Filling:
In a mixing bowl, beat the softened cream cheese and powdered sugar until smooth and fluffy.
Add the pureed strawberries, vanilla extract, and lemon juice (if using). Mix until well combined.
Transfer the filling into a piping bag or plastic sandwich bag with the tip cut off.
Assemble the Donuts:
Once the donuts have cooled slightly, use a skewer or knife to make a small hole in the side of each donut.
Pipe the strawberry cheesecake filling into each donut, filling it generously.
In a shallow dish, combine the sugar and cinnamon. Roll each filled donut in the sugar mixture for a sweet coating.
Serve:
Serve the stuffed donuts warm and enjoy the sweet, creamy strawberry cheesecake filling!