Preheat oven to 325°. Toast **3 Tbsp. pecans** on a small rimmed baking sheet, tossing halfway through, until slightly darkened in color and fragrant, 10–12 minutes. Let cool, then coarsely chop.
 
#### Step 2
Heat **4 Tbsp. unsalted butter, cut into pieces**, **¼ cup (packed; 50 g) dark brown sugar**, **½ tsp. ground cinnamon**, and **¼ tsp. ground cardamom**in a medium skillet over medium-high, whisking constantly as the mixture bubbles, until butter is melted and incorporated, about 1 minute. Add **½ tsp. vanilla extract** and cook sauce, continuing to whisk, until slightly thickened, about 30 seconds.
 
#### Step 3
Arrange **2 bananas, halved lengthwise, then crosswise**, cut side down, in pan and cook, shaking pan occasionally, until lightly browned, 30–60 seconds. Using tongs or a small spatula, turn bananas over and sprinkle cut sides with **kosher salt**. Cook, shaking pan occasionally, until bananas are browned and coated in sauce, 30–60 seconds. Remove from heat.
 
#### Step 4
Drizzle **3 Tbsp. dark rum (80–100 proof)** over bananas and sauce. Using lighter, carefully ignite sauce and flambé, shaking pan occasionally, until flame goes out.
 
#### Step 5
Top with scoops of **vanilla ice cream** and scatter pecans over.