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 ‘White Onion’
(sold as Bermuda White, Granex white, Snow white, Southport white, Sweet Spanish, Spanish)

Family: Amaryllidaceae

Common names: COCKTAIL ONION, PICKLING ONION, SHORT DAY WHITE ONION, WHITE 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: 100

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

All of these are white/off white onions - a vetted list of bulbs for the home garden. Other common names that apply are listed adjacent to a selling name for these bulbs:
Sweet Spanish, Spanish -- LONG DAY white/off white ONION, Spanish Onion
Southport white/off white globe -- LONG DAY white/off white ONION, GLOBE
Snow white/off white -- LONG DAY white/off white ONION, SHORT DAY white/off white ONION
Granex white/off white -- SHORT DAY white/off white ONION
Bermuda white/off white -- SHORT DAY white/off white ONION, PICKLING ONION, COCKTAIL ONION

As a flowering plant these onions appeal to a few 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