PREHEAT THE OVEN TO 350 AND GREASE A 9×13 CASSEROLE BAKING PAN.
COMBINE FLOUR, BOTH SUGARS, BAKING SODA, PECANS, AND CINNAMON ON A LARGE MIXING BOWL.
IN A SEPARATE BOWL, WHISK TOGETHER OIL, EGGS, VANILLA EXTRACT, CRUSHED PINEAPPLE AND SMASHED BANANAS. WHISK UNTIL ALL COMBINED.
POUR WET INGREDIENTS INTO THE DRY INGREDIENTS. MIX WITH A SPATULA UNTIL SMOOTHLY COMBINED.
POUR CAKE BATTER INTO THE PREPARED BAKING PAN AND SPREAD IT EVENLY.
BAKE FOR 40-45 MINUTES.
LET THE CAKE COOL FOR ABOUT 10 MINUTES. POKE HOLES ALL OVER THE CAKE (USE SOMETHING THAT IS ABOUT A PENCIL THICKNESS).
IN A MIXING BOWL, WHISK SWEETENED CONDENSED MILK, PINEAPPLE, CINNAMON, AND COOL WHIP (IF USING) TOGETHER.
EVENLY, POUR SWEET SAUCE MIXTURE ALL OVER THE CAKE. LET IT SEEP IN AND COOL COMPLETELY BEFORE FROSTING.
FROSTING
BEAT BUTTER AND CREAM CHEESE TOGETHER, ON MEDIUM-HIGH SPEED, UNTIL SMOOTH, 1-2 MINUTES. SCRAPE SIDES AND BOTTOM OF THE BOWL.
LOWER THE SPEED TO LOW AND BEAT-IN POWDER SUGAR, CINNAMON, PECANS, AND VANILLA EXTRACT.
TURN THE SPEED BACK UP TO MEDIUM-HIGH AND BEAT FOR ABOUT 3-4 MINUTES, UNTIL THE FROSTING IS LIGHT, SMOOTH AND FLUFFY.
ONCE THE CAKE IS COOLED, EVENLY FROST THE CAKE ALL OVER.
OPTIONAL: SPREAD CHOPPED PECANS ALL OVER THE TOP OF THE FROSTED CAKE.
COVER AND KEEP THE CAKE REFRIGERATED WHEN NOT SERVING.