1 box lemon cake mix
1/2 cup butter, softened
1/2 cup oil
1/2 cup freshly squeezed orange juice, strained to remove seeds and pulp
2 cups (8 to 10) mandarin oranges, peeled, seeded, pith and membranes removed, and finely chopped (or two 11-ounce cans mandarin oranges in light syrup, drained)
2 T. finely grated orange peel (mandarin or other)
2 T. cornstarch
3 T. sugar
1-1/2 cup sifted powdered sugar
1-1/2 T. freshly squeezed lemon juice, strained to remove seeds and pulp
1 T. light corn syrup
For the filling, puree oranges and zest until smooth; place in heavy-bottomed saucepan. In a separate bowl, combine cornstarch and sugar, mixing well to remove any lumps.
Over medium-high heat, bring orange mixture to a boil. Stir cornstarch and sugar mixture into the oranges. Reduce heat to medium; cook and stir until thickened and bubbly. Continue to cook and stir for 2 minutes more. Remove from heat and let cool.
For the cake, place all ingredients in large mixing bowl and beat on low speed for 30 seconds or until ingredients are just combined. Beat for 2 minutes on high speed, scraping bowl occasionally.
Pour batter into a greased bundt pan. Spoon filling on top of batter, forming a ring in the center of the batter. Bake at 350 degrees until toothpick inserted comes out clean, about 45 minutes. Cool on a wire rack for 15 minutes; remove cake from pan by inverting onto wire rack. Cool thoroughly.
For the glaze, whisk together ingredients until smooth and spoon over top of cooled cake. Glaze will run down sides. Serves 12 to 14.