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

In a stand mixer, combine one egg, brown sugar, granulated sugar, Greek yogurt, avocado oil, melted butter, milk, and vanilla extract. Mix on medium speed until creamy, about 2 minutes.

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

Gradually add the dry mixture to the wet ingredients while mixing on low speed until just combined.

Scoop the batter evenly into muffin liners, filling each about two-thirds of the way full.

In another bowl, mix cream cheese with an egg and sugar until smooth. Spoon over the batter in each muffin liner.

For the crumble topping, combine flour, brown sugar, cinnamon, and melted butter until you achieve a wet-sand texture. Sprinkle over each cream cheese layer.

Bake for 25-30 minutes, checking doneness with a toothpick.

Remove from the oven and allow to cool in the pan for 10 minutes before transferring to a wire rack.