Preheat the oven to 350°F. 

Generously grease a 9-inch round cake pan. 

Cut a piece of parchment paper to fit the bottom of the pan then use it to line the pan; set aside. 

In a small bowl, stir together heavy cream and sugar until combined. 

Spread mixture evenly over bottom of pan; set aside.

Melt butter in a large skillet over medium high heat. 

Arrange pears in skillet in a single layer and cook, flipping once, until edges are deep golden brown, 2 to 3 minutes per side. 

Remove from heat and set pears aside to let cool slightly. 

Arrange pears in the bottom of the pan in a decorative pattern then sprinkle with walnuts.

In a medium bowl, prepare cake mix according to package directions. 

Pour batter over pears and smooth out with the back of a spoon. 

Bake until a toothpick inserted into the center comes out clean, 40 to 45 minutes. 

Transfer pan to rack to let cool then run a knife around edge of cake to release it from pan. 

Invert cake onto a plate, remove and discard parchment paper, cut cake into slices and serve.