Mix the base: In a bowl, whisk Greek yogurt, vanilla, sweetener, and a pinch of salt until smooth.
Add protein (optional): Stir in the protein powder. If it gets too thick, add a splash of milk until creamy.
Create the cinnamon swirl: In a small cup, mix cinnamon with a little sweetener and a teaspoon of water or maple syrup to make a pourable paste.
Swirl it in: Spoon the cinnamon mixture over the yogurt and gently swirl with a knife or spoon.
Top it off: Add fruit, nuts, or granola as desired.
Keep it lighter with fruit or go indulgent with a small crunch topping.
Optional icing: Combine 1 tablespoon light cream cheese, 1 teaspoon milk, a drop of vanilla, and a touch of sweetener. Drizzle over the top.