Preheat the oven to 350 F.: You will notice the oven warming and a gentle dry heat that is ideal for even cooking. Setting the oven to 350 F creates a steady environment so the loaf cooks through without the exterior burning before the center sets. Listen for the faint hum of the oven as it regulates, and be sure the rack is centered for uniform heat circulation. A common mistake is not allowing the oven to fully come to temperature, which can lead to undercooked centers; avoid this by preheating for at least 10 minutes and using an oven thermometer if your oven runs cool or hot.
Remove flesh from sweet potato, discard skin and mash in a large bowl.: When you scoop out the warm sweet potato , the aroma is slightly caramelized and sweet, and the flesh should be soft enough to mash with minimal effort. Use a fork to break it down until it is mostly smooth, leaving only a few small lumps for texture if you like. This step matters because the consistency of the sweet potato determines the loafs moisture level and how well the mixture binds. If the potato is too chunky, the loaf may not hold together; if it is too wet, it can become gummy. A typical problem is leaving the potato too cool which makes it harder to mash, so work with it warm or room temperature for best results.
Add turkey, egg, dried onion, 1/4 cup ketchup, marjoram and 1 teaspoon kosher salt, and mix with the ground turkey using a fork until mixed well.: After adding the ground turkey , egg , dried onion flakes , ketchup , marjoram , and kosher salt , you will feel the mixture change from separate elements into a cohesive batter. Mixing with a fork gives gentle control so you do not overwork the meat, which would make the loaf dense. As you combine, note the scent of sweet and savory balancing, and press a small portion between your fingers to check the texture; it should be moist but not soupy. A frequent error is vigorous mixing which tightens the proteins and leads to dryness, so fold until just combined.
In a small bowl combine 2 tablespoons of the ketchup with Worcestershire sauce.: This quick glaze is glossy and slightly tangy, and the aroma of Worcestershire sauce will lift the sweetness of the ketchup . Whisking briefly emulsifies them so the sauce spreads smoothly across the loaf later. The purpose is to create a finishing layer that caramelizes on top during baking, adding visual appeal and flavor contrast. If you skip this step or apply it unevenly, the top can bake without that sticky glaze, so take a moment to get a homogeneous mixture and spoon it evenly when called for.
Shape into a loaf and place on a baking sheet. Spoon sauce on top.: As you shape the mixture into a neat loaf, you should feel it hold together, with slight give when pressed, indicating the balance of binder and protein is correct. Place it on a prepared sheet pan so heat can surround the loaf for even browning. Spoon the glaze across the top in a thin, even layer; you will see a glossy sheen that promises caramelization. Visual cues include smooth edges and a uniformly coated top. One common issue is shaping the loaf too tightly, which reduces tenderness, so handle it gently to keep air pockets that help a pleasant texture.
Bake uncovered for 55 minutes, remove from oven and let it sit for 5 minutes before slicing.: During baking you will notice the top deepening in color and the glaze bubbling slightly, and the kitchen will fill with roasted sweet notes. Cooking for 55 minutes at 350 F allows the loaf to reach a safe internal temperature while developing a firm exterior. After removing it from the oven, the resting period is crucial; it lets juices redistribute so slices hold shape and are not watery. A common mistake is slicing immediately, which can lead to crumbling and loss of juices, so wait the full five minutes for best results.