Preheat oven to 400''F. (205''C.). In a bowl, combine flour, salt and chili seasoning. Cut in margarine and lard until mixture resembles bread crumbs. Add cheese and mix well. Stir in cold water and mix to form a fairly firm dough. Knead gently on a floured surface and roll out pastry. Set a 10" flouted flan pan with a removable bottom on a baking sheet. Press pastry into flutes and trim edge neatly. Prick base with a fork. Line pastry with waxed paper and fill with dried beans.
Bake 15 minutes. Remove waxed paper and beans and bake 5-10 minutes more or until dry and lightly golden. Fry bacon 3 minutes. Add onion; cook 2 minutes. Remove from heat; mix with crabmeat. Spoon mixture into flan shell. Whisk eggs, half-and-half, mustard, cayenne and salt. Pour into flan shell. Bake 30-35 minutes or until set and lightly golden. Garnish with tomato and parsley, if desired, and serve warm or cold.