Combine 1 cup all-purpose flour, undissolved yeast, poppy seed, sugar and salt in a large bowl. Add very warm water and oil; mix until well blended, about 1 minute. Gradually add enough remaining flour to make a soft dough. Dough should form a ball and will be slightly sticky. Knead** on a floured surface, adding additional flour if necessary, until smooth and elastic, about 4 minutes. Cover and let rest on floured surface while preparing toppings.
Slice hot dogs into 1/4-inch thick slices. Set aside.
Pat dough with floured hands to fill greased pizza pan or baking sheet. OR roll dough on a floured counter to a 12-inch circle; place in greased pizza pan or baking sheet. Form a rim by pinching the edge of the dough.
Spread mustard evenly over pizza dough. Top with relish and hot dogs. Sprinkle with cheese.
Bake on lowest rack for 12 to 15 minutes, until cheese is bubbly and crust is lightly browned.
Combine onion, dill pickles and sport peppers in a medium mixing bowl while pizza is baking. Stir in celery salt; set aside.
Remove pizza from oven; set on wire rack. Cool 5 minutes. Strain onion mixture (if needed) and spread evenly over top of pizza. Garnish with tomato wedges.
*If you don't have a thermometer, water should feel very warm to the touch.
**To knead the dough, add just enough flour to the dough and your hands to keep the dough from sticking. Flatten dough and fold it toward you.Using the heels of your hands, push the dough away with a rolling motion. Rotate dough a quarter turn and repeat the "fold, push and turn" steps. Keep kneading dough until it is smooth and elastic. Use a little more flour if dough becomes too sticky, always working the flour into the ball of dough.
***If Chicago-style relish not available, substitute with sweet relish and stir in 3 drops yellow food coloring and 2 drops blue food coloring. It may be necessary to strain relish if too much juice.
Recipe Note: Sport peppers are available, jarred, in the condiment section of the grocery store. If unavailable, pepperoncini peppers may be substituted.