Wet the top of the glass with lime juice and roll the glass in Tajin, then set aside.

Add 1 sliced or cubed fresh mango to a blender and blend on high until smooth puree forms. Transfer the mixture to a bowl and set aside.

Add the tequila, mango puree, simple syrup, and ice to a shaker and shake well for 10 seconds until chilled.

Pour the cocktail into an Old Fashioned glass over ice. Top the cocktail off with hard cider and garnish with fresh mango slices.