I have always thought a guavadilla to be a cross between a guava and a granadilla – turns out its just a yellow variety of the purple granadilla just bigger and smooth skinned, although I must say that the yellow variety does smell like a guava where as the purple variety doesn’t. I’m sure if I try hard enough I can even taste a wee bit of guava in the yellow ones too. They grow in abundance here in our little village and Steff from our garden service was kind enough to share some of his loot with us and even did a second trip to bring me some of the vine for my photos. Thanks Steff! Think I shall make some guavadilla infused cupcakes.
Passiflora edulis is a vine species of passion flower that is native to Paraguay, Brazil and northern Argentina (Corrientes and Misiones provinces, among others). Its common names include passion fruit (UK and US), and passionfruit (Australia and New Zealand), purple granadilla and maracuja. In Colombia, the purple passion fruit is referred to as “gulupa”, to distinguish it from the yellow maracuyá.
In South Africa, passion fruit, known locally as Granadilla (the yellow variety as Guavadilla), is used to flavour yogurt. It is also used to flavour soft drinks such as Schweppes Sparkling Granadilla and numerous cordial drinks. It is often eaten raw or used as a topping for cakes and tarts. Granadilla juice is commonly available in restaurants. The yellow variety is used for juice processing, while the purple variety is sold in fresh fruit markets.
It is cultivated commercially in warmer, frost-free areas for its fruit and is widely grown in India, Sri Lanka, New Zealand, the Caribbean, Brazil, Colombia, Bolivia, Ecuador, Indonesia, Peru, Puerto Rico, Dominican Republic, California, Florida, Haiti, Hawaii, Argentina, Australia, East Africa, Mexico, Israel, Costa Rica, Venezuela, South Africa and Portugal.
The passion fruit is round to oval, either yellow or dark purple at maturity, with a soft to firm, juicy interior filled with numerous seeds. The fruit is both eaten and juiced; passion fruit juice is often added to other fruit juices to enhance the aroma.
The two types of passion fruit have clearly differing exterior appearances. The bright yellow variety of passion fruit, which is also known as the Golden Passion Fruit, can grow up to the size of a grapefruit, has a smooth, glossy, light and airy rind, and has been used as a rootstock for the Purple Passion Fruit in Australia. The dark purple passion fruit is smaller than a lemon, though it is less acidic than the yellow passion fruit, and has a richer aroma and flavour. It tastes like lemons, guava and pineapple combined. 
Fresh passion fruit is high in beta carotene, potassium, and dietary fibre. Passion fruit juice is a good source of ascorbic acid (vitamin C), and good for people who have high blood pressure. Some research is showing that purple passion fruit peel may help with controlling asthma symptoms. The fruit contains Lycopene in the mature and immature pericarp.
Information sourced from Wipipedia.