Preheat your oven to 350°F and position a rack in the middle. While the oven heats, prepare your loaf pan by greasing it generously with oil or cooking spray, then dust it lightly with flour, tapping out any excess. Roughly chop the walnuts into 1/4-inch pieces and slice the rhubarb into 1/2-inch thick pieces, keeping a few nicer slices aside for topping. Prepare your two flax eggs by mixing 1 tablespoon ground flaxseed with 3 tablespoons water per egg and let them sit for 5 minutes to thicken—this gives them binding power similar to regular eggs.

In a pot over medium heat, add the sliced rhubarb with just a splash of water (about 1/4 cup). Cook for 12-15 minutes, stirring occasionally, until the rhubarb breaks down and releases its juice—you want some pieces to lose their shape while maintaining some texture. This cooking step is crucial because it releases moisture and concentrates the rhubarb flavor while preventing the bread from becoming too wet. Set the cooked rhubarb aside to cool slightly while you prepare the dry ingredients.

In a large mixing bowl, whisk together the flour, baking powder, baking soda, salt, sugar, cinnamon, and chopped walnuts. Make sure the baking soda and baking powder are evenly distributed throughout the flour—this prevents any concentrated pockets of bitter flavor or uneven rise. I like to whisk these dry ingredients thoroughly because it aerates the flour and ensures the leavening agents are well-distributed, which gives you a more even crumb structure.

In a second bowl, combine the avocado oil, prepared flax eggs, and the cooked rhubarb from Step 2. Stir until the mixture is well combined and relatively smooth, though some rhubarb pieces breaking apart is fine. The flax eggs will help bind everything together and provide structure to the bread, while the oil adds moisture and richness.

Pour the wet mixture from Step 4 into the bowl with the dry ingredients from Step 3. Using a spatula or wooden spoon, gently fold everything together until just combined—don't overmix, as this can develop gluten and make the bread tough. The batter should look slightly lumpy, which is perfect. Pour the batter into your prepared loaf pan and smooth the top with a spatula.

Place the loaf pan in the preheated 350°F oven and bake for 50-60 minutes. The bread is done when a toothpick inserted into the center comes out with just a few moist crumbs (not wet batter). I typically check at the 48-minute mark to avoid overbaking, since every oven varies slightly. The top should be golden brown and the edges should pull slightly away from the sides of the pan.

Remove the bread from the oven and let it cool in the pan for 30 minutes—this resting time allows the crumb structure to set properly so it doesn't fall apart when you turn it out. After 30 minutes, run a thin knife around the edges to loosen it, then turn the pan upside down onto a wire rack to release the bread completely. Let it cool to room temperature on the rack before slicing.