Preheat oven to 350 degrees. Spray a loaf pan with nonstick cooking spray and line with parchment paper. Set aside. (I used a 8.5 x 4.5 x 2.75 inch loaf pan, but any pan you have is fine! If it's larger, the baking time will be less, if it's smaller, the baking time will be more.): When you start here, you should notice the oven warming and a faint metallic tang from initial heating, which signals a steady heat environment. Preheating ensures the chemical leaveners react properly right away, creating lift rather than slow expansion that yields a dense center. Lining with parchment gives you clean edges and easy removal, while nonstick spray prevents the paper from sliding. One common mistake is skipping preheat, which can make the loaf underbaked in the middle while the outside darkens too quickly. Another thing to watch is pan size, because visual cues like the top taking on a golden hue are tied to oven temperature and pan dimensions.
In a large bowl, stir truvia, sugar, oil, applesauce, egg whites, vanilla and yogurt together. Add in remaining dry ingredients and stir until just incorporated. Scrape the sides of the bowl to ensure batter is well mixed. Pour into prepared loaf pan and smooth the top.: At this stage the bowl will smell sweet and warmly spiced once the vanilla and cinnamon mingle with the applesauce . Mixing the wet ingredients first produces a glossy, cohesive batter base that traps moisture. Folding in the dry ingredients briefly keeps the gluten from overdeveloping, maintaining tenderness. Use a spatula to scrape the sides so you don't leave pockets of flour at the bottom, which can create dry streaks. Avoid overmixing, which causes a gummy texture and dense crumb. The correct visual cue is a batter that is smooth with small pockets of air, not a completely deflated paste.
In a small bowl, stir melted butter together with brown sugar, oats, flour and cinnamon to create a crumbly topping. Sprinkle evenly over the batter and bake 45-55 minutes. (Mine was done right at 50 minutes.): When combining the streusel, the aromas of toasted butter and brown sugar should be noticeable, even before baking. The mixture should clump slightly when pressed between fingers but still fall apart easily, indicating the right balance of fat and dry ingredients. Even sprinkling ensures each slice has streusel coverage that toasts uniformly. As the loaf bakes, listen for faint settling sounds and watch for the top to turn a deep golden brown with edges pulling slightly away from the pan. A common issue is applying a streusel that is too wet, which can sink into the batter instead of toasting on top. If you see the top browning too quickly, tent the loaf with foil to prevent overbrowning while the center finishes baking.
Remove from oven, cool at least 15 minutes before removing from pan and cooling completely (or mostly cool). Slice into 12 even slices and enjoy. Store remaining applesauce streusel bread in an airtight container for up to 3 days. Makes great french toast!: As the loaf comes out of the oven you should notice a rich, spiced aroma and a gently domed top that feels set when lightly pressed. Cooling for at least 15 minutes lets steam redistribute so the loaf firms up and slices cleanly. If you try to unmold while piping hot, the crumb can tear and be gummy. Visual cues for doneness include a deep golden top and a toothpick inserted near the center coming out with a few moist crumbs but not wet batter. Allowing it to cool completely improves slicing and texture, while storing in an airtight container maintains freshness. A common mistake is storing while still warm, which creates condensation and a soggy crust. For best results, cool fully and then slice evenly into 12 portions as intended.