Preheat your oven to 350°F and grease a 9x5 inch loaf pan or similar-sized bread pan with butter or cooking spray. Chop the rhubarb into 1/2-inch pieces and set aside. Measure out all your dry ingredients (flour, baking powder, baking soda, salt) into one bowl, and gather your wet ingredients nearby. Having everything ready before you start mixing will ensure a smooth baking process.

In a small bowl, combine the cold butter cubes, brown sugar, flour, cinnamon, salt, and lemon zest. Using a fork or your fingertips, work the cold butter into the dry mixture until it resembles coarse breadcrumbs with pea-sized pieces of butter throughout. This crumble texture is crucial—the cold butter creates pockets that stay distinct during baking rather than fully incorporating into the mixture. Set the crumble aside while you prepare the batter.

In a large mixing bowl, cream together the softened butter and sugar for about 1 minute using an electric mixer or by hand, until the mixture is light and fluffy. This aerating step is important—it helps incorporate air into the batter, which creates a lighter, more tender crumb in the final bread. Stop and scrape down the sides of the bowl as needed.

Add the room-temperature eggs one at a time, beating well after each addition to fully incorporate. Then add the Greek yogurt and vanilla extract, stirring until just combined—about 30 seconds total for this step. I like using Fage yogurt here because its tangy richness adds depth to the bread's flavor while keeping it wonderfully moist. Don't overmix once the yogurt is added, as you want to maintain some of that air you worked to incorporate in the previous step.

Add the dry ingredient mixture from Step 1 to the wet ingredients, folding gently with a spatula until just combined. The batter should come together without any visible dry streaks, but don't overmix—overmixing develops gluten and leads to a dense, tough bread. A few small lumps are perfectly fine and actually preferable to overdoing it.

Fold the chopped rhubarb gently into the batter from Step 5. Pour half of the batter into your prepared pan, then sprinkle half of the crumble topping from Step 2 evenly over it. Add the remaining batter on top, and finish with the rest of the crumble topping. Bake on the bottom rack of your preheated oven for 65-70 minutes, rotating the pan halfway through (around the 35-minute mark) to ensure even browning. The bread is done when a toothpick inserted into the center comes out with just a few moist crumbs clinging to it, and the top is golden brown.

Remove the bread from the oven and let it cool in the pan for about 10-15 minutes, then turn it out onto a wire rack to cool completely. This short cooling period in the pan helps the bread set, making it easier to turn out without it falling apart. Once cooled, slice and enjoy—this bread stays wonderfully moist for several days when wrapped and stored at room temperature.