Mix the yeast and warm water in a small bowl and let it sit while you mix the other liquids. This gives the yeast a head start, away from the salt, which retards its growth.
Melt the butter in a small saucepan or in the microwave (in short bursts, watching it so that it doesn't burn). Beat the eggs in a large bowl. (You may not be able to use your hand mixer for this, unless it can handle extra-large batches of dough.) Add the evaporated milk, sugar, and salt. Mix in the butter, which should have cooled down. Finally, add the dissolved yeast. Add a cup or two of the flour to the butter and egg mixture and mix. Add some of the pumpkin puree and mix. Alternate adding flour and puree until all of the flour and the puree have been added to the dough. Cover the bowl and put it in a warm spot to rise. Let it rise for about 1 hour, or until the dough has doubled in size. Heat the oil in your deep-fryer or large pot to 350 degrees. Add a few scoops of dough to the oil. Fry the malasadas until they're golden brown. Drain the cooked malasadas on paper towels. Roll in a pan of granulated sugar, or shake in a bag full of sugar.