In small saucepan, add cranberries, 1 Tbsp water, and monk fruit powder. Bring to a simmer over medium-high heat. Once simmering, reduce heat to medium-low and allow mixture to cook, stirring often, until cranberries have popped, and mixture has thickened slightly. Stir in arrowroot mixture and continue to cook, stirring constantly for 1 minute. Remove saucepan from heat and set aside, allowing mixture to cool for 10 minutes. Pour cranberry filling into crust and spread into even layer. Place tart in refrigerator while making topping.