Sprinkle the yeast over the water in a large mixing bowl and stir to dissolve. Using a wooden spoon, beat in the eggs, pumpkin, soft butter, sugar, salt, thyme and cayenne. Add 3 cups of flour and beat until smooth, gradually adding more flour as needed to make a soft, sticky but still manageable dough. Make sure the dough is well mixed. Oil a larger bowl and scrape the dough into it, turning to oil all sides. Cover with a dish towel and let rise in a warm, draft-free spot until doubled in bulk, about 1 1/2 hours. Punch the dough down, cover tightly with plastic wrap and refrigerate overnight.