Prepare the Streusel Topping by combining flour, sugar, and salt in a bowl. Add melted butter and mix until crumbly. Set aside.

Mix the dry ingredients in another bowl: flour, baking powder, and salt. Whisk until evenly distributed.

In a large bowl, mix the wet ingredients: egg, sugar, vegetable oil, vanilla extract, and Greek yogurt. Whisk until smooth.

Combine the dry ingredients with the wet mixture, stirring until just combined. The batter should be slightly lumpy.

Gently fold in the diced strawberries, ensuring they are evenly distributed in the batter.

Create the cream cheese filling by beating together cream cheese, sugar, vanilla extract, and cornstarch until smooth.

Preheat the oven to 425°F and prepare muffin tins. Spoon batter into cups, add cream cheese filling, and top with streusel.

Bake the muffins at 425°F for 5 minutes, then lower to 350°F and bake for another 22-25 minutes until golden brown.

Let the muffins cool in the pan for 5 minutes before transferring to a wire rack. Serve warm or allow to cool completely.