Preheat oven to 350 degrees F (175 degrees C). Grease and flour two 9x5-inch loaf pans.

Beat vegetable oil and sugar together in a bowl until creamy and smooth; stir in eggs.

Mash bananas and lemon juice together in a separate bowl; mix into oil mixture until just incorporated.

Sift flour, baking powder, and salt together in a third bowl. Slowly mix into the wet mixture using an electric mixer on low until just incorporated; do not overmix. Fold in walnuts. Pour batter into the two prepared loaf pans.

Bake in the preheated oven until a toothpick inserted in the center of the loaf comes out somewhat clean, about 1 hour 15 minutes. If the toothpick comes out clean, you have overcooked the bread.