REGIONAL FOOD FAVORITES by mail (or more likely, UPS or Federal Express) have become an almost universal marketing tool. This week it's Arizona Gourmet Traders, "purveyors of fine Southwest food products."

A half dozen sampler baskets are offered with such products as blue corn tortilla chips and blue corn muffin mix, margarita marmalade, mustard sauces, black-bean-and-red-chili sauce, barbecue glazes and, of course, salsas.

While the brochure is free, as is the telephone call to 1-800-228-4952, the baskets are not cheap. But then, there's nothing like goodies from home.

ARE FOOD STORES getting smaller, or are we getting bigger? According to an annual study ("Facts About Store Development") by the Food Marketing Institute, the typical new supermarket that opened last year was 40,000 square feet, down 800 square feet from 1988, which was down significantly from an all-time high of 46,892 square feet in 1987.

Don't be fooled, however, by the short-term trend. Even with that drop, the new stores of the '80s are far larger than those being built 10 years ago, when the average new supermarket was 33,000 square feet.

And, back in the '50s, the average new grocery was but 13,600 square feet. It's a good thing they didn't have to find room for the microwave pizza display case.

TO DO...

Thursday-Oct. 14: "Foods of Spain" promotion at area Sutton Place Gourmet stores, with afternoon tapas parties, cooking demonstrations and sangria tastings. Call (301) 231-5050 for locations and hours.

Friday-Sunday: Greek Village Festival and Agora, noon to 9 p.m., food, wines, music and dancing, to benefit Greek cardiac patients at the National Institutes of Health, Greek Orthodox Church of St. George, 7701 Bradley Blvd., Bethesda. Call (301) 469-7990 for information.

WHAT HAS FRANK SINATRA been up to lately? Give up? Well, it seems Old Blue Eyes has been in the kitchen -- mixing up tomato sauces, of all things -- and now these sauces are for sale.

We tried Marinara With Mushrooms and found it to be light but flavorful, with chunks of fresh-tasting tomatoes throughout. Two other sauces, Milano Style and Tomato Basil With Parmesan, complete the line from Artanis (that's Sinatra spelled backward, you see).

Unlike Paul Newman's venture into foods, however, Sinatra's sauces are strictly for profit. The sauces are currently available at Bradley's Food & Beverage, 6904 Arlington Rd., Bethesda; (301) 654-6966.

SALMON WITH MUSTARD SAUCE (4 servings)

This quick-to-make mustard cream sauce is a savory way to enhance fresh salmon fillets (or grilled shrimp). With the fish, serve steamed new potatoes and broccoli or zucchini.

2 teaspoons freshly squeezed lemon juice

4 6-ounce boned salmon fillets, skin on

2 tablespoons grated onion

2 shallots, minced

Salt and freshly ground pepper, to taste

FOR THE MUSTARD SAUCE:

2 teaspoons honey mustard

1 1/2 teaspoons Dijon or Creole mustard

Several squirts liquid hot pepper sauce, or to taste

1/2 cup heavy cream

1 tablespoon unsalted butter, softened

Preheat the broiler to high. Sprinkle the lemon juice over the salmon flesh; rub with the grated onion and shallots. Season with salt and pepper. Broil the salmon for 5 to 7 minutes, or until cooked through, but still moist.

Make the mustard sauce while the salmon is cooking: Combine both mustards, hot pepper sauce and heavy cream in a small saucepan; set over moderate heat and cook until hot. Off the heat, whisk in the butter.

Place the salmon fillets on warm plates. Spoon some of the sauce over each piece of fish. Serve immediately.

Per serving: 438 calories, 48 gm protein, 3 gm carbohydrates, 25 gm fat, 10 gm saturated fat, 128 mg cholesterol, 197 mg sodium. -- Lisa Yockelson

BEST HOUSEHOLD HINT of the week has not been tested. The reason being, of course, if it didn't work we couldn't print it.

Anyway, this one's just too good to pass up. Columnist John Lehndorff of the Daily Camera in Boulder, Colo., recently lamented the "progressive flavor and texture mutations" that a slowly consumed, home-delivered pizza goes through as it cools, "from steamy, painfully hot through warm and redolent to congealed and chewy."

A reader suggested that such deterioration in edibility could be delayed by placing the pizza box on an electric heating pad.