Preheat oven to 375 degrees.
Cook 1 cup sugar in a dry 2-quart heavy saucepan over moderately-low heat, stirring slowly with a fork, until melted and pale golden. Cook caramel without stirring, swirling pan, until deep golden, about 5 minutes.
Quickly and carefully remove hot dish from oven and immediately pour caramel into dish, tilting it to cover bottom and sides. (Leave oven on.) Keep tilting as caramel cools and thickens enough to stay in place.
Scald whole milk with evaporated milk in a saucepan and remove from heat. Beat eggs and remaining cup sugar with an electric mixer until smooth and creamy. Beat in salt, pumpkin, tequila, and spices. Pour milk mixture through a sieve into a bowl and beat into pumpkin mixture in a slow stream until combined well.
Pour custard over caramel in dish and set in a water bath of 1-inch hot water. Put pan in middle of oven and lower temperature to 350 degrees. Bake until golden brown on top and a knife inserted in center comes out clean, about 1 1/4 hours, possibly longer. Remove dish from water bath and transfer to a rack to cool. Chill flan, covered, until cold, at least 6 hours.
To unmold flan, dip bottom of souffle dish briefly (20 to 30 seconds) in a warm water bath. Then, run a thin knife around flan to loosen from sides of dish. Wiggle dish from side to side and, when flan moves freely in dish, invert a large serving platter with a lip over dish. Holding dish and platter securely together, quickly invert and turn out flan onto platter. Caramel will pour out over and around it. Cut flan into wedges and serve with caramel spooned over and with shards of Pumpkin Seed Praline.
For the Pumpkin Seed Praline: Preheat oven to 250 degrees. Lightly oil a large sheet of foil on a baking sheet and keep warm in oven.
Cook sugar, water, and a pinch of salt in a deep 2-quart heavy saucepan over moderately-low heat, stirring slowly with a metal fork, until melted and pale golden. Cook caramel without stirring, swirling pan, until deep golden.
Immediately stir in pumpkin seeds and quickly pour onto foil, spreading into a thin sheet before it hardens. (If caramel hardens and is difficult to spread, put in a 400 degree oven until warm enough to spread, 1 to 2 minutes.)
Cool praline on baking sheet on a rack until completely hardened, then break into large pieces This recipe yields 8 to 10 servings.