In small bowl, stir sour cream and 1 tablespoon brown sugar. In large skillet, melt butter over medium-high heat; add remaining 1/3 cup brown sugar and cook 1 minute, stirring occasionally. Add mangoes; cook 3 minutes or until mangoes begin to soften. Carefully add tequila; with long-handled lighter, ignite mangoes. Remove from heat; let flame burn out.
Serve mango mixture drizzled with sour cream mixture sprinkled with lime zest and cinnamon, if desired.