1Spray bottom and sides of 8x4-inch loaf pan with cooking spray (without flour). In small bowl, mix water and yeast; set aside. In another small bowl, mix all flours, the salt, baking powder, xanthan gum and guar gum; set aside.
2In medium bowl, beat eggs, sugar, oil and vinegar with electric mixer on medium speed 1 to 2 minutes. Beat in yeast mixture. Add flour mixture; beat on medium speed until thoroughly mixed. Pour into pan.
3Spray top of dough with cooking spray (without flour); if necessary, smooth top of dough with spatula. Cover with plastic wrap; let rise in warm place (80°F to 85°F) 1 hour to 1 hour 30 minutes or until dough rises to top of pan.
4Heat oven to 375°F. Carefully remove plastic wrap from pan; bake 30 minutes. Reduce oven temperature to 350°F. Cover loaf with cooking parchment paper; bake 25 to 30 minutes longer or until instant-read thermometer inserted in center of loaf reads 207°F. Cool 5 minutes; remove from pan to cooling rack. Cool completely, about 40 minutes.