Cut sweet potato into 1/2-inch-thick slices and punch out heart shapes with a cookie cutter. Put the hearts in a quart-size ziplock bag with 2 teaspoons olive oil and salt to taste. Seal the bag, then shake it to coat the hearts.
Arrange the hearts in a single layer on a foil-lined cookie sheet and bake at 400°, turning once, until the potatoes are soft and golden brown, about 30 minutes.
Combine 1/4 cup yogurt, maple syrup, and cinnamon.