Either use store bought, cubed mango or fresh. For fresh whole mango (See Note 1).
Heat mango juice, sugar, lemon juice, and 1 cup water in saucepan over medium-high heat, stirring until sugar dissolves. Transfer mixture to a bowl or 4-cup measuring bowl. Refrigerate until chilled.
Stir 1 cup diced mango (save remaining for other use) and ancho chili powder into the chilled mixture and pour into eight 3-ounce ice-pop molds. Top with cover and insert wooden sticks or handles that come with your ice-pop mold kit. Transfer molds to the freezer for 3 hours or more.
If you don't have a mold kit with a top lid that positions the wooden popsicle sticks, transfer molds to the freezer and freeze until slightly slushy, about 1 hour. Insert a popsicle stick into each mold and freeze until ice pops are solid, about 3 hours or more.
To release ice pops from molds, run the bottom of the molds briefly under warm water and push up from bottom. Serve with a sprinkle of tajin on top (optional).
Notes
Hold the mango upright and find the tallest side. The pit will be sitting along that line, so you’ll want to be facing parallel to that side. With a small paring knife, carefully slice half of the mango off of the pit, turn mango and remove other side. Discard the pit. Carefully cut lines vertically and horizontally through the mango side of each half without cutting through the skin. Turn mango half inside-out by pressing the skin side outward with your thumbs, exposing the cubed mango. Take a paring knife and carefully slice off the cubes of mango or use a spoon and scoop them out before turning inside-out.