In a large bowl, combine butter and cake mix; mix at low speed until well blended. The mixture will be crumbly. Add pretzels and mix well. Press in bottom of pan. Bake at 350 for 12 minutes. Let cool 5 minutes.
In a large bowl, combine sugar, corn syrup, and 2 eggs; mix at low speed until well blended. Stir in remaining filling ingredients. Spoon evenly over partially baked crust.
Return to oven; bake an additional 30 to 40 minutes or until edges are deep golden brown (center will not be set). Cool 10 minutes. Run knife around sides of pan to loosen. Cool 1 hour or until completely cooled. Cut into bars. Store in loosely covered container.