In a medium bowl, whisk together pecans, brown sugar, and cinnamon. In a large bowl, mix flour, baking powder, baking soda, butter, granulated sugar, and vanilla until well combined, then. Add sour cream and eggs and beat until a smooth batter is formed.
Spray a 7-cup Bundt pan with nonstick cooking spray. Place half of the pecan mixture in prepared pan, then pour batter on top. Top with remaining pecan mixture. Cover pan tightly with aluminum foil.
Pour water into an Instant Pot® and place the trivet in the pot, then place Bundt pan on trivet. Place the lid on the Instant Pot® and click into place to close. Press the Pressure Cook button and adjust the timer to 40 Minutes. When the timer beeps, let the pressure release naturally for 10 Minutes, then quick-release any remaining pressure until float valve drops. Unlock lid. When done, cake should feel firm, and a toothpick inserted into the center should come out clean. Let cake cool 20 Minutes, then invert onto a plate to serve.