Preheat your oven to 350°F (175°C) and line a 6-cup muffin tin with paper liners.

In a stand mixer, combine egg, brown sugar, granulated sugar, Greek yogurt, avocado oil, melted butter, milk, and vanilla extract; blend on medium speed for 2-3 minutes until smooth.

In a separate bowl, whisk together gluten-free flour, baking soda, baking powder, salt, and cinnamon.

Gradually add the dry mixture to the wet mixture and mix gently until just combined.

Evenly distribute the muffin batter into the prepared liners, filling each about two-thirds full.

In a bowl, mix softened cream cheese, the remaining egg, and a bit of sugar; spoon this mixture over the muffin batter.

Combine topping flour, brown sugar, cinnamon, and melted butter in a small bowl; blend until it resembles wet sand and sprinkle it over the cream cheese layer.

Bake for 25-30 minutes, check for doneness by inserting a toothpick into the center.

Let the muffins cool in the pan for about 10 minutes, then transfer to a wire rack to cool completely.