Combine buttermilk, honey, and butter in a microwave-safe bowl; heat in microwave in 30 second increments until temperature is just below 110 degrees F (43 degrees C).
Pour buttermilk mixture into the bowl of a stand mixer and add whole wheat flour, all-purpose flour, wheat gluten, yeast, lecithin, salt, ginger, and vitamin C powder; mix, using the dough hook attachment on low speed, until dough just holds together and sides of bowl are clean. Let dough rest in bowl for 2 minutes; mix again with the dough hook attachment for 2 minutes more.
Remove dough from bowl and knead by hand on a work surface until dough is warm and elastic, 2 to 3 minutes.
Spray a large bowl with cooking spray and place dough in the bowl, turning it to coat all sides with oil. Spray a piece of plastic wrap with cooking spray and cover bowl with sprayed-side down. Let dough rise until doubled in size, about 1 hour.
Gently deflate dough by pressing with your fingers and let rise 10 to 15 minutes more.
Turn dough onto a work surface and roll into an 8 1/2x11-inch rectangle. Starting with the short end, roll dough tightly into a roll, pinching the seams shut. Fold the ends underneath the loaf, pinching the edges to form a smooth top.
Spray a loaf pan with cooking spray and place loaf in the pan. Cover dough loosely with the sprayed-plastic wrap. Let dough rise 1 1/2 to 2 inches above the pan, 30 to 45 minutes.
Preheat oven to 350 degrees F (175 degrees C). Remove plastic wrap from loaf.
Bake in the preheated oven for 35 to 40 minutes. Flip bread out of pan using hot pads; internal temperature should read 190 degrees F (88 degrees C). Allow loaf to cool on wire rack before slicing.