Zinnia
Butterflies in Mind -- Zinnia
Susan C. Dunlap
A collection of 50 images as if seen from a butterfly’s point of view. Includes the names of native Zinnia species and the most complete list of US butterflies that will feed on Zinnia blossoms.
Asclepias
Butterflies in Mind -- Asclepias
Susan C. Dunlap
“Milkweed is the single most important plant for Monarch butterflies. This lavishly illustrated book contains details about the structure and cultivation of native Milkweeds, information about the 139 nectar-feeding butterflies they...
Monarch
Butterflies in Mind -- Monarch
Susan C. Dunlap
This abundantly illustrated volume enables you to select from a complete list of well described perennial nectar plants that are known to attract & feed Monarch butterflies. Over 40 genera are described that are suitable to be grown...
Perennials
Butterflies in Mind -- Perennials
Susan C. Dunlap
Butterflies in Mind - Perennials. This book is a definitive guide to perennial nectar plants preferred by US butterflies. It empowers you to feed, attract, support (and help identify) nectar-feeding butterflies that reside in the US....

Allium cepa ‘Yellow Onion’
(sold as Ailsa Craig, Rijnsburger, Sweet & Early, Fiesta, Candy Yellow, Ebenezer Yellow, Sweet Spanish Yellow, Bermuda Yellow, Texas Grano, Texas grano 1015y, Texas supersweet, Vidalia, Walla Walla, Granex Yellow)

Family: Amaryllidaceae

Common names: EARLY BULB, SHORT DAY YELLOW ONION, YELLOW ONION

Native to: Not Known In The Wild

Sentiment: prosperity

Plant

Types: biennial, perennial

Forms: erect, tufted

Max height: 4 feet

Max width: 1.75 feet

Flower

white/off white

Leaf

green

Horticulture

Attracts wildlife: adult butterfly, bee, specific butterfly species

Seedling days to mature: 110

Edible: vegetable

Exposure: sun

Propagates by: seed

flowers in summer

Soil type: average

USDA Zones: zone 5 to -20 f, zone 6 to -10 f, zone 7 to 0 f, zone 8 to +10 f, zone 9 to +20 f

Temp. range: -20 to +30 °F

Water: dry, regular

Allium cepa is the scientific name for cooking onions including - white, yellow, red, bunching onions, and shallots.

Below is a vetted list of yellow onion bulbs useful to the home gardener:
Walla Walla Onion SWEET ONION, YELLOW ONION, LONG DAY YELLOW ONION
Ailsa Craig YELLOW ONION
Rijnsburger YELLOW ONION
Sweet & Early YELLOW ONION
Fiesta YELLOW ONION, LATE BULB
Candy Yellow YELLOW ONION, LONG DAY YELLOW ONION
Ebenezer Yellow YELLOW ONION, LONG DAY YELLOW ONION
Sweet Spanish Yellow YELLOW ONION, LONG DAY YELLOW ONION
Bermuda Yellow YELLOW ONION, SHORT DAY YELLOW ONION
Texas Grano YELLOW ONION, SHORT DAY YELLOW ONION
Texas grano 1015y YELLOW ONION, SHORT DAY YELLOW ONION
Texas supersweet YELLOW ONION, SHORT DAY YELLOW ONION
Vidalia YELLOW ONION, SHORT DAY YELLOW ONION
Granex Yellow YELLOW ONION, SHORT DAY YELLOW ONION, EARLY BULB

This flowering plant appeals to many nectar-feeding butterflies:
Abaeis nicippe
Aglais urticae
Ascia monuste
Euphydryas chalcedona
Euptoieta claudia
Hesperia sassacus
Hylephila phyleus
Junonia coenia 
Nathalis iole
Panoquina panoquin
Papilio glaucus
Papilio xuthus
Pholisora catullus
Piruna pirus
Poanes melane
Poanes zabulon
Vanessa cardui